what's wrong with me? Codeforces 877B - Nikita and String Codeforces 489B - BerSU Ball - Involves sorting. Similar idea to DSU solution. $$$\frac{MOD + 1}{2}$$$ is the inverse of $$$2$$$ for any odd modulo. EDIT: Was able to solve it. can anyone please explain how, dp is working in the f question how they ended up with these three equations?? is this valid input? Solutions for the codeforces.com problemset section exercises. In the first test i have 10 different numbers, but also the number 11. i have checked for all pairs (i,j) such that $$$i+j=k-1$$$. Can anyone explain what type of function is this in the editorial of B? Actually I think this contest is really good. So this schedule would burn about 1,100 calories a week (studies show that burning 1,000 to 2,000 calories a week in exercise helps protect against heart disease). time limit per test. Also my second question that if the cat is at the same position with Alice after moving a,b,c and d moves that means the cat is safe and not being lost then again, WHY should it print a NO?? Tutorial. it’s little foggy in editorial. Do it for all i's from 1 to k/2 and summed up the answer along the way.75164924, Refer https://codeforces.com/blog/entry/75432?#comment-595594. In 1989, a study was completed by the Cooper Institute that linked daily walking … Thank you so much! After that I assigned characters to each disjoint set greedily. blog for matrix and binary exponentiation. It’s easy to bump up your pace and go longer distances as you get better. You can see my code, maybe you will understand. Her current position $$$(u, v)$$$ should always satisfy the constraints: $$$x_1 \le u \le x_2$$$, $$$y_1 \le v \le y_2$$$. What will be the correct DP algorithm for the D problem I want tabulation method correct algorithm for finding the path for a given grid where the and of all the element on the grid is maximum as possible, If anyone is interested in detailed explanation of Problem D, https://competitiveprogrammingdiscuss.blogspot.com/2020/04/codeforces-round-630-div-2-problem-d.html, i can't understand the editorial solution of 1332C problem. TruaTheOrca. Why it isn't working? As the C++ solution illustrates, an odd $$$k$$$ in problem C does not need to be treated separately, despite what the tutorial says. Alice can do the moves in any order. The only programming contests Web 2.0 platform $$$(a+b)^n=\sum\limits_{i=0}^n\tbinom{n}{i}a^{n-i}b^i$$$, $$$(a-b)^n=\sum\limits_{i=0}^n\tbinom{n}{i}a^{n-i}(-1)^ib^i$$$, Then we have $$$(a+b)^n-(a-b)^n=\sum\limits_{i=0}^n\tbinom{n}{i}a^{n-i}(1-(-1)^i)b^i$$$, If i is even, then $$$1-(-1)^i=0$$$,else $$$1-(-1)^i=2$$$. Then why does it prints a no. thanks for pointing it out. Is B solvable using graph coloring where edge exist between two elements if their gcd is 1. i don't know how you do the graph coloring. I think I understand discrete binary search (about monotonicity of the sequence for some predicate.. but I think that's standard and commonplace) but I need to master the details so that I can solve problems that aren't "apparent to involve anything with binary search yet does so beautifully". in this case and $$$i=1$$$, you are supposed to pick 3 and 7 instead of the second top element of the stack which should be 4 and 6 if you follow the implementation the code presents. I'm just curious in problem d ..since that dp algorithm fails...could there be a different dp approach which would actually lead to a correct solution triple__a ? These masks would work great for a brisk walk or other lower-intensity workout since they fit close to your face. Understand the basics about exercise and chronic disease. Sorry, I got mixed up between your and editorials formula. Thanks. Codeshows 100DaysOfCode repository. Get started today.Physical activity doesn't need to be complicated. I could avoid this division by 2 by not overcounting in the first place. Then you look for the most frequent amongst all of these and change all 4 to this character. So $$$r - l + 1 = M$$$ and $$$n m = 2 (M - 1)$$$The answer should be $$$M^{2 (M-1)} \mod M = 0$$$.But if you use $$$b\mod \phi(M)$$$ as the exponent, you are computing $$$0^0$$$ and the code returns 1 instead. Dont answer the above query I have solved it. It works for c-d. That's why I am asking why it doesn't work for d-c. d is for moving along positive y direction and c is for moving along negative y direction why would you subtract your current position(initial y) with d and add it with c,rather you are supposed to do the opposite(which is y+d-c=y-(c-d))..it's so obvious. Any operation we make doesn't change the parity of such a sum. This mission is the penultimate mission in The Truth mission series. Walk down to the height min(h 2, h 3), ... and so on. The point is that if we modify a valid grid with this algorithm, the corresponding invalid grid should also get modified to that exact valid grid (I mean that's why I called that "pair up"). Then the set of all grids such that $$$a_{0, 0} = k$$$ remains unmatched. I think you misunderstood the question, its not about checking weather the final position of the cat is safe instead the cat needs to be safe in the whole jurney. CodeForces Problems. I think the below data should be another answer but it is giving me wrong answer on this?? Could someone kindly explain 4th problem ? Here's my submission 74980482. Let me appreciate the fact, Problem E was really nice!! I have used the exact same method as stated in the editorial for Question B — Composite Coloring but I got one of the test cases (not pretests) wrong. Illustration about Walk on the elliptical trainer. 1. But can you explain what is the correct approach to find maximum answer using DP because bob's approach is incorrect. It seems like it should be 2*(dpv1 +dpv0 — dpv) as it can come from cases when dpu is either coloured or uncoloured. If you like the video, please subscribe and leave a like (and 一键三连)! (Let the modulo be $$$M = 998244353$$$). I think this explains it Link to geeksforgeeks.org, This should help: https://www.youtube.com/watch?v=GU7DpgHINWQ. For example, $$$(1 + x)^{2} = 1 + 2x + x^{2}$$$ will be simply $$$2 + 2x$$$. (Code). Therefore at least one of them is smaller than $$$\sqrt{1000}$$$, and from now on let's consider that $$$b\leq\sqrt{1000}$$$. So difference between optimal way and dp way is less than k. In the problem it is mentioned that all numbers can be in range [0, 300000], Yes, but the question was about range [0, 100'000], triple__a Thanks for such a good round in these days!! So $$$(a+b)^n-(a-b)^n=\sum\limits_{i=1,3,5,...}^{i\leq n}2\tbinom{n}{i}a^{n-i}b^i$$$. Now we know that for any given $$$a$$$, there is always a prime number smaller than $$$\sqrt{1000}$$$ which divides it. Or we need other method to pair those grids? Try to walk briskly for at least half an hour every day, or one hour four times a week. Codeforces. So do I. 1. 144,457,129 stock photos online. Never use someone else's code, read the tutorials or communicate with other person during a virtual contest. since you should do carefully when $$$R=c[L]$$$. For every character in position i, you're collecting all i+kth chars, and also finding the mirror positioned chars for each of them. This obviously requires the routes not to go through cells which already have height R. "You want to connect these up into k pairs such that the routes connecting different pairs are not crossing(i.e. need to be identical as well, Now find the character that's used most frequently, and change the remaining characters to that, For eg., consider "abcbaa" and k = 3. 512 megabytes. I realized that R is only a bound in the beginning. What is it's implications? Can anyone tell me why my code was wrong? Nothing to learn. The staring point is $$$(x, y)$$$. Ilya and a Colorful Walk programming blog. Thanks in Advance, https://competitiveprogrammingdiscuss.blogspot.com/2020/04/codeforces-round-630-div-2-problem-c.html. Programming competitions and contests, programming community. kindly verify it by checking against following test case, in solution to prob C I am not able to understand this ---> "To minimize the required number of changes, you should make all the letters equal to the one which appears at these positions the most initially", The only programming contests Web 2.0 platform. Complexity will be $$$O(\log nm)$$$ with binary exponentiation. Condition 1: A/c to question indices i, i+k, i+2k.... should have the same char at their index. so something like (k-1,0) and (0,k-1) will be both counted. But why include dpv in dpv1 rather than exclude dpv from dpv1 directly? We may keep doing this until only the grid with $$$a_{i,j}=k$$$ for all $$$(i,j)$$$ remains. Define polynomial multiplication like this: $$$x^{i} \times x^{j} = x^{(i + j) \mod 2}$$$. It'll be an easier approach. I am getting answer 17 for test case. I first want to say that I'm just new to the site and really impressed of the quality of contents on it. Never . please , would anyone like to explain it ? Modification of the algorithms for directed graphs is left as an exercise for the reader. Let $$$a$$$ be one such integer, $$$a \leq 1000$$$. Programming competitions and contests, programming community. Hope you could provide one that does what the solution says. Codeforces. What is the general thought process for approaching constructive algorithm based question. Honestly, it doesn't matter that much what algorithm you choose to match them. Now I think you are coping with equal elements. Thanks in advance. A. Those are constraints given in the question. And I understand the part "It is fine for it to be isolated from bottom when it is connected to its parent by an edge.". I know its trivial but,Can you please tell me the intuition behind Problem B? I didn't got why are we using (x2>x1||a+b==0)&&(y2>y1||c+d==0) condition?? Codeforces 577B -Modulo Sum - Involves digits. To keep her cat fit, Alice wants to design an exercising walk for her cat! An alternative solution for D. Consider the example —, The algorithm uses: 11111 -> 10000 -> 11111 -> 1001, answer = 0 Optimal answer: 11111 -> 1111 -> 11111 -> 1001, answer = k, Can anyone pls explain me what the code snippet does or provide any link understand the coding. a[0], a[3], a[5], a[2] which are "a", "b", "a" and "c" respectively. Obviously, every integer from [1..xy] occurs exactly once in this matrix. We can start by assigning each position of the string as a disjoint set. Isn't that wrong? Div1 A / … In Problem E, It's mentioned that There is a general solution for this kind of problems.Can anyone provide any resource and more problems like that? I will solve recent problems from Codeforces, mainly around div2D difficulty. I was initially contributing to the Daily-Coding-Problems repository for my daily practice. "Walk around the block, or better yet, ‘walk to work’ every morning." Can anyone explain how the dp formula in problem F works in detail? thanks for tutorial solutions in (PYTHON). The intuitive part is that imagining all combinations of numbers, something like half of them will be even (we're looking for evens because there needs to be an even amount of odds, so sum has to be even). It works only if $$$(MOD + 1)$$$ is divisible by $$$X$$$ — then $$$\dfrac{MOD + 1}{X} \cdot X \equiv 1 \pmod{MOD}$$$. Nice round! Like what is the actual fault in Bob algo and why his algo not able to achieve optimal answer. The simplest form of exercise that everyone should do while fasting is walking. Can you explain more how to recover the min/max after we got the first and last index in a k=4 sequence? If you don't like the video, leave your suggestions in the comment area below! It was like hit or miss. And how you are coming up with the matrix given in editorial. The editorial is not at all clear to me. can you explain that special case, please.How x1>x2 can be fixed with a+b=0? My browser it not loading Mathematical Equations/Symbols. You are correct, both the x and y-axis have to be considered. Also since its a palindrome, the mirror character for each of these characters (i.e. 2) C. Matrix Walk. GitHub is home to over 50 million developers working together to host and review code, manage projects, and build software together. A 200 pages book that gives a brief view of how people of Okinawa-Japan, stay happy, physically fit and live way longer than the rest of the world. 1332A - Exercising Walk. Walk up the tree to the top and eat a nut. Atcoder Beginner Contest 189 Post-contest Discussion, Contributor of idea of the solution: awoo. Strong legs will help you get faster and walk longer. standard output. Just register for practice and you will be able to submit solutions. - evilsocket/codeforces Use Git or checkout with SVN using the web URL. Bullet screens and comments are welcomed. At last, replace flag array with tmp array to check the next bit. The cat is initially at x=1, and it is given that a=1 and b=1 so the cat now needs to move to x=0 or x=2 both of which are not 'safe' hence the answer is NO. https://codeforces.com/contest/1332/submission/75045994, In question A, why don't we add an or condition for the y-axis also? It's just equivalent transformation. To begin, this post has nothing to do with the contest (i just need help with a topic is all).. Walking can actually be considered a full body exercise. 2) Finished → Virtual participation ... To keep her cat fit, Alice wants to design an exercising walk for her cat! I just want to know the ideas here, or it's just happen to be this way. I think the proof of observation 2 assumes this is always possible. Codeforces Round #193 (Div. Jump to the tree 2. https://ideone.com/zhB5cl. 1. The round definitely made me think (and question my existence). Make a HEALTHY CHOICE today and WALK with us! This is just the binomial expansion, $$$ (x+y)^n = \sum\limits_{i=0}^{n}{ n \choose i } {x^i y^{n-i} } $$$. Hello everyone ! Let's take a more simple problem say you have an empty grid and you have 2 * k marked cells in this grid. You can just draw it out, like for these grids: There's 4 grids for the first one and half of them are even, and there's 9 grids for the second one and (9+1)/2 of them are even. it is now fixed. In problem B I used following code , but it isn't working, Can anyone help me? I was initially contributing to the Daily-Coding-Problems repository for my daily practice. Thanks again. 30 minutes of fast walking everyday is so HEALTHY! time limit per test. When including dpu in dpu1, it actually includes case where u is isolated and colored. You said that only one grid can't be paired but I can't figured out which one. Just take a Hamiltonian path in the grid(not too hard to find one) and pair up the elements along this path. Think how the DP approach might give a nonoptimal result. Thanks a lot. Similarly, for the case where there is at least one edge from v to a child, we consider both cases for each child of whether to include it or not and subtract the cases when we don't include any one of them (inclusion-exclusion). Codeforces. https://codeforces.com/contest/1332/submission/75023756, I implement DSU but it fails. Which you all the best (and stay at home :p)! Kudos, I have done c using dsu it is efficient in this manner. So now you can check out my solution that uses matrix multiplication:74968680. All 4 are already the same and nothing else needs to be done. So dpu0 means we don't choose point u(no matter add edges or not), dpu1 means we must choose point u(no matter add edges or not), and dpu means for all sons of point u, we don't add the edge (u, v)? but anyone did it using dp or is it not possible ? CodeLink. So the only case that can't be matched is that all the cell is $$$k$$$ right? I would like to specify the explanation under the problem 1332E - Height All the Same, on the Easy intuition solution: The case when k is even seems to me not clear enough and can be misleading. Robot from (0,0), he can only up the 'U' or right 'R' walk Coordinate system with a lot of parcels, respectively, at some point The robot needs to go past all these parcels are collected I know either way it's needed to deal with dpv. I think the bits are not independent. (i) with (n+1−i) and (i) with (k+i) now each connected component of the graph will have same value in the final string. Thank you OP and every organizers for the contest ;). According to the problem statement, "for each color from 1 to m there is at least one element of this color". You can prove by induction that $$$dp_{even}[i] - dp_{odd}[i] = (-1)^i$$$ if $$$L, R$$$ are odd, $$$(-1)^{i+1}$$$ if $$$L, R$$$ are even, $$$0$$$ otherwise. I am not satisfied with the pretests of C. My $$$O(n^2)$$$ solution passed them. I have taken a little while to realize this, now it's nice that you have fixed it! Although the locomotion comes from the work the legs are doing, the arms still have to swing, and the core still has to work to stabilize you while you’re moving. So I don't think it could get TLE. The link to my submission: 76447494. I assumed it would be like that for all grids. I meant that if R is a bound in the beginning and the end as well and you have n * m % 2 == 1, L = 0 and R = 2 and an even number of 1s and an odd number of 0s you have to be able to connect them pairwise without crossing. It's because each set of points is visited twice. The pre-calculation costs only 202ms on test 109, and answering a query only needs constant time. Case 57 is 998244352 2 1 998244353. Not a member of Pastebin yet? Now you have to count how many letters should be the same in this cycle. I'm trying to understand the solution of 1332E - Height All the Same. Is walking exercise? But no node comes in my brain... Basically for each i in range 1 <= i <= n — k , s[i] = s[n + 1 — i] , and s[i] = s[i + k]. Then maybe my bad day, but somehow in any contest pikemike is involved i end up not even solving A. :(. Initially, Alice's cat is located in a cell $$$(x,y)$$$ of an infinite grid. Because $$$a_i\leq 1000$$$, while in other problems $$$a_i$$$ is always $$$\leq 10^9$$$. text 0.85 KB . They call it Ikigai, that’s what makes their lives… Learn more.. Open with GitHub Desktop Download ZIP Fortunately first one where I get it accepted (at least on pretests), but I still have no idea what the solution is, I copied M arcin_smu's code from Petrozavodsk (Winter 2016 problem J2) and made some adjustments :P. It appeared on some Topcoder as well, but I couldn't find it (iirc setter was Lewin) Walk up the tree to the top and eat a nut. If we were to complete the game, as there is an even number of cells, the sum of all of them would be even, which in our case won't ever happen ! You mean dpv1 also counts the case that v is colored but isolated from all its children? In problem D could some one tell what's the problem in that matrix? I removed b % phi(mod) in the power function and it passed. Consider c[x] the I'm a fool. I solved F in this way.dp[0][x] and dp[1][x] mean the results in x's subtree and x in edge induced subgraphs.than the subtree combine with the father and add to the father node so I get this: initially, every node's dp[0][x]=1; dp[1][x]=1; for example,1-2,2-3,2-4, first 3 and 4 node are both (1,1), than in node 2, first I choose the 3 to mix 2 ,node 2 get (3,2) ,means now 2-3 this tree's ,with node 2 in edge induced subgraphs, results .than mix 4 to 2 ,get node 2 (9,4) as the question required, add all dp[0][x] and dp[1][x] to answer and remove the one node set , so ans-=2*n it shows right in two examples. For problem F, don't we need to consider stack overflow when using recursive dfs since n <= 3e5? Watch Queue Queue Watch Queue Queue. Now, that we have the info about the connected components we can easily find the char which has occurred the most number of times in that component. No you need dpv to be in dpv1 because those cases will be used for the parent of v. It is fine for it to be isolated from bottom when it is connected to its parent by an edge. Codeforces Round #630 (Div. So you can do dfs an find which positions should have same characters and calculate the answer based on which character appears the most times on each group. I saw your solution for this problem I must it's very easy to understand just one query why are we outputing ans/2 in the end instead of ans. As my question below, it will be easier to understand dpu1 if it excludes dpu in the first place. Want to solve the contest problems after the official contest ends? Illustration of trainer, bodybuilding, target - 44124256 The number of self-employed people aged 65 and over has more than doubled in the past five years. I don't have many ideas when I meet the constructive algorithm problems. I want to learn "binary search the answer" and other details of the algorithm, I tried searching the internet and Codeforces blogs but couldn't find anything specific to the topic that I was looking for.. so the index should be i c[i] and those two if $$$b$$$ starts with $$$a[i]$$$. sorry for forgetting this comment, today someone reminded me. You can do as much as you can squeeze in, because fasted walking isn’t just easy and not stressful—it’s anti-stress. I suggest you to re-read the question. 3) The next and final iteration (i=2) would consider the same four elements as the first iteration. After these operations, our DSU will provide which all indices belong to the same connected component. ok, I get it.edge induced subgraphs isn't connected graph . Can you help Alice find out if there exists a walk satisfying her wishes? This is what my code do. And it turns out there are only $$$11$$$ primes that meet this requirement !
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