题目传送门 /* 贪心:每次把一个丢掉,选择最小的.累加求和,重复n-1次 */ /************************************************ Author :Running_Time Created Time :2015-8-1 13:20:01 File Name :A.cpp *************************************************/ #include <cstdio> #include <algori…

http://codeforces.com/contest/461 A.水题 B.太挫了,竟然被hack了一发.... C.贪心..竟然没看出来时哈夫曼编码问题 D.题目大意:给一棵树,每一个点为白色或黑色,切断一些边,使得每一个连通块有且仅有一个黑点,问划分方案数. 树形DP, 设状态: dp[v][0]表示以v为根的子树中没有黑点,dp[v][1]有一个黑点. 状态方程: dp[v][1] = dp[v][1]*dp[son][0] + dp[v][0]*dp[son][1] + dp[v]…

B 树形dp 组合的思想. Z队长的思路. dp[i][1]表示以i为跟结点的子树向上贡献1个的方案,dp[i][0]表示以i为跟结点的子树向上贡献0个的方案. 如果当前为叶子节点,dp[i][0] = 1,(颜色为1,可以断开与父节点的连接,颜色为0,不断开,方案恒为1),dp[i][1] = co[i](i节点的颜色). 非叶子节点:将所有孩子节点的dp[child][0]乘起来为sum,孩子贡献为0的总方案. 当前颜色为0时, dp[i][1] += sum/dp[child][0]*dp…

题意:给了一棵树以及每个节点的颜色,1代表黑,0代表白,求将这棵树拆成k棵树,使得每棵树恰好有一个黑色节点的方法数 解法:树形DP问题.定义: dp[u][0]表示以u为根的子树对父亲的贡献为0 dp[u][1]表示以u为根的子树对父亲的贡献为1 现在假设u为白色,它的子树有x,y,z,那么有 dp[u][1]+=dp[x][1]*dp[y][0]*dp[z][0]+dp[x][0]*dp[y][1]*dp[z][0]+dp[x][0]*dp[y][0]*dp[z][1] dp[u][0]+=d…

题意: 给出一棵树,每个节点都被标记了黑或白色,要求把这棵树的其中k条变切换,划分成k+1棵子树,每颗子树必须有1个黑色节点,求有多少种划分方法. 题解: 树形dp dp[x][0]表示是以x为根的树形成一块不含黑色点的方案数 dp[x][1]表示是以x为根的树形成一块含一个黑色点方案数 //зїеп:1085422276 #include <cstdio> #include <cmath> #include <cstring> #include <ctime&g…

吐槽:一辈子要在DIV 2混了. A,B,C都是简单题,看AC人数就知道了. A:如果我们定义数组为N*N的话就不用考虑边界了 #include<iostream> #include <string> #include <vector> #include<cstring> #include<cstdio> #include<cmath> #include<string> #include<algorithm>…

题目链接 D. Appleman and Tree time limit per test :2 seconds memory limit per test: 256 megabytes input :standard input output:standard output Appleman has a tree with n vertices. Some of the vertices (at least one) are colored black and other vertices a…

题目链接 A. Appleman and Easy Task time limit per test:2 secondsmemory limit per test:256 megabytesinput:standard inputoutput:standard output Toastman came up with a very easy task. He gives it to Appleman, but Appleman doesn't know how to solve it. Can…

C. Appleman and a Sheet of Paper   Appleman has a very big sheet of paper. This sheet has a form of rectangle with dimensions 1 × n. Your task is help Appleman with folding of such a sheet. Actually, you need to perform q queries. Each query will hav…

题目: C. Appleman and Toastman time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output Appleman and Toastman play a game. Initially Appleman gives one group of n numbers to the Toastman, then they s…