随笔分类 - CodeForces
摘要：The graph is called tree if it is connected and has no cycles. Suppose the tree is rooted at some vertex. Then tree is called to be perfect k k -ary t
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摘要：One of Arkady's friends works at a huge radio telescope. A few decades ago the telescope has sent a signal s s towards a faraway galaxy. Recently they
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摘要：题意：N个人排成一行，分成K组，要求每组的不和谐值之和最小。 思路：开始以为是斜率优化DP，但是每个区间的值其实已经知道了，即是没有和下标有关的未知数了，所以没必要用斜率。 四边形优化。 dp[i][j]表示前j个人分为i组的最小代价。 622ms 利用DP决策单调性解决：684ms。二者时间差不多
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摘要：题意：长度为n的排列，m次交换xi, yi，每个交换x，y有50%的概率不发生，问逆序数的期望 。n, m <= 1000 思路：我们只用维护大小关系，dp[i][j]表示位置i的数比位置j的数大的概率。 那么每次交换x和y。 假设x<y，那么区间就有三种: [1,x-1]，[x+1,y-1]， [
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摘要：A thief made his way to a shop. As usual he has his lucky knapsack with him. The knapsack can contain k objects. There are n kinds of products in the
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摘要：As you know, the game of "Nim" is played with n piles of stones, where the i-th pile initially contains ai stones. Two players alternate the turns. Du
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摘要：You are given a string ss. You should answer nn queries. The ii-th query consists of integer kiki and string mimi. The answer for this query is the mi
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摘要：Yash is finally tired of computing the length of the longest Fibonacci-ish sequence. He now plays around with more complex things such as Fibonacci-is
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摘要：At the children's day, the child came to Picks's house, and messed his house up. Picks was angry at him. A lot of important things were lost, in parti
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摘要：There are well-known formulas: , , . Also mathematicians found similar formulas for higher degrees. Find the value of the sum modulo 109 + 7 (so you s
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摘要：Let's call a non-empty sequence of positive integers a1, a2... ak coprime if the greatest common divisor of all elements of this sequence is equal to
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摘要：You are given n points on Cartesian plane. Every point is a lattice point (i. e. both of its coordinates are integers), and all points are distinct. Y
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摘要：Little Petya likes to draw. He drew N red and M blue points on the plane in such a way that no three points lie on the same line. Now he wonders what
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摘要：题意：给定N个点，用矩形将所有点覆盖，要求矩形宽度最小。 思路：裸体，旋转卡壳去rotate即可。 最远距离是点到点；宽度是点到边。
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摘要：You are given n points with integer coordinates on the plane. Points are given in a way such that there is no triangle, formed by any three of these n
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摘要：Count the number of distinct sequences a1, a2, ..., an (1 ≤ ai) consisting of positive integers such that gcd(a1, a2, ..., an) = x and . As this numbe
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摘要：Lakhesh loves to make movies, so Nephren helps her run a cinema. We may call it No. 68 Cinema. However, one day, the No. 68 Cinema runs out of changes
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摘要：Ivan had string s consisting of small English letters. However, his friend Julia decided to make fun of him and hid the string s. Ivan preferred makin
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摘要：Vasya has decided to build a zip-line on trees of a nearby forest. He wants the line to be as long as possible but he doesn't remember exactly the hei
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摘要：Vasya's telephone contains n photos. Photo number 1 is currently opened on the phone. It is allowed to move left and right to the adjacent photo by sw
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