题意 分别算一个树中所有简单路径长度模3为0,1,2的距离和乘2. 分析 记录两个数组, \(dp[i][k]\)为距i模3为k的子节点到i的距离和 \(f[i][k]\)为距i模3为k的子节点的个数 \(ans[k]\)为所有简单路径长度模3为k的距离和 \(v\)是\(u\)的儿子,\(c\)是u到v的边长度,\(0<i,j<3,k=(j-c\%3+3)\%3\) \(dp[u][(i+c\%3)\%3]+=dp[v][i]+f[v][i]*c\) \(f[u][(i+c\%3)\%3]+…

题目传送门 题意:求一颗树中所有点对(a,b)的路径长度,路径长度按照模3之后的值进行分类,最后分别求每一类的和 分析:树形DP \(dp[i][j]\) 表示以 i 为根的子树中,所有子节点到 i 的路径长度模3等于 j 的路径之和 \(c[i][j]\) 表示以 i 为根的子树中,所有子节点到 i 的路径长度模3等于 j 的点数 \(ok[i][j]\) 表示以 i 为根的子树中,是否有子节点到 i 的路径长度模3等于 j 每次只考虑所有经过根 x 的路径,并且路径的一个端点在 x 的一颗子…

链接: https://nanti.jisuanke.com/t/41403 题意: State Z is a underwater kingdom of the Atlantic Ocean. This country is amazing. There are nn cities in the country and n-1n−1 undirected underwater roads which connect all cities. In order to save energy and…

链接: https://nanti.jisuanke.com/t/41402 题意: To seek candies for Maomao, Dudu comes to a maze. There are nn rooms numbered from 11 to nn and mm undirected roads. There are two kinds of rooms in the maze -- candy room and monster room. There is one cand…

题意:有一棵n个点的树,点之间用无向边相连.现把这棵树对应一个序列,这个序列任意两点的距离为这两点在树上的距离,显然,这样的序列有n!个,加入这是第i个序列,那么这个序列所提供的贡献值为:第一个点到其他所有点距离之和.求所有序列贡献值之和. 思路:假如第一个点是k,那么后面n-1个点共有(n - 1)!种排列,也就是说,第一个点是k那么这样的序列的贡献值为(n - 1)!*(k到其他点距离之和),显然最后答案应该是所有点之间的距离和的两倍 *(n - 1)!.问题转化为了求一棵树上所有点之间的距…

Fish eating fruit \[ Time Limit: 1000 ms \quad Memory Limit: 262144 kB \] 题意 大体的题意就是给出一棵树,求每一对点之间的距离,然后把该距离存在距离 \(\mod 3\) 的位置,输出总和. 思路 令两个 \(dp\) 数组和两个辅助 \(dp\) 的数组. \(dp1[i][j]\) 表示从 \(i\) 为起点往下到各个点距离 \(\mod 3\) 后为 \(j\) 的距离总和. \(cnt1[i][j]\) 表示以 \…

2018 ICPC 沈阳网络赛 Call of Accepted 题目描述:求一个算式的最大值与最小值. solution 按普通算式计算方法做,只不过要同时记住最大值和最小值而已. Convex Hull 题目描述:定义函数\(gay(x)\),若\(x\)是某个非\(1\)的数的平方的倍数,则\(gay(x)=0\),否则\(gay(x)=x^2\),求\(\sum_{num=1}^{n} ( \sum_{i=1}^{num} gay(x) ) mod p\) solution \[\sum…

线段树+单调栈+前缀和--2019icpc南昌网络赛I Alice has a magic array. She suggests that the value of a interval is equal to the sum of the values in the interval, multiplied by the smallest value in the interval. Now she is planning to find the max value of the inter…

2019ICPC南京网络赛A题 The beautiful values of the palace https://nanti.jisuanke.com/t/41298 Here is a square matrix of n * nn∗n, each lattice has its value (nn must be odd), and the center value is n * nn∗n. Its spiral decline along the center of the squar…

"Oh, There is a bipartite graph.""Make it Fantastic." X wants to check whether a bipartite graph is a fantastic graph. He has two fantastic numbers, and he wants to let all the degrees to between the two boundaries. You can pick up sev…