题意:排序二叉树按照数插入的顺序不同会出现不同的结构,现在要在1~m选n个数,使按顺序插入形成的结构与给出的结构相同,有多少种选法. 解法:先将给出的结构插入,构造出一棵排序二叉树,再dfs统计,首先赋ans = C(m,n),从m个数中取n个数,然后将这n个数安排插入顺序,dfs,如果此时节点左右子树都有,那么其实左右子树的插入顺序可以相间,所有就是一个排列保持相对顺序不变地插入另一个保持相对顺序不变的序列中,有多少种插入方法呢,如果一个序列个数为k1,另一个为k2,那么方法数为:C(k1+k…

B - Counting BST Time Limit:3000MS     Memory Limit:0KB     64bit IO Format:%lld & %llu Submit Status Practice UVALive 5058 Description Binary Search Tree (BST) is a rooted binary tree data structure which has following properties: Left subtree conta…

题目链接:https://icpcarchive.ecs.baylor.edu/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=1296 题意:给出一个a*b的网格,在网格上取不共线的三点构成三角形,求三角形总数.分析:就是一一道简单的组合数计算题目,设总结点数为n,则取三个节点的个数为C(n,3), 然后减去横向.竖向.斜向的三点共线的个数即可,斜线三点共线等价于所枚举的矩形的长宽成倍数关系,…

题目:http://poj.org/problem?id=3046 就是多重集组合数(分组背包优化): 从式子角度考虑:(干脆看这篇博客) https://blog.csdn.net/viphong/article/details/48110525 从意义的角度来考虑: 当 j<=a[i] 时,f[i][j] = f[i-1][j]  + f[i][j-1],就是分成了不选第 i 种物品和至少选一个第 i 种物品的情况,其中 f[i][j-1] 代表 j-1 后剩下的那一个物品一定是第 i 种:…

题意 : 有 n 种蚂蚁,第 i 种蚂蚁有ai个,一共有 A 个蚂蚁.不同类别的蚂蚁可以相互区分,但同种类别的蚂蚁不能相互区别.从这些蚂蚁中分别取出S,S+1...B个,一共有多少种取法. 分析 :  实际就是要解决 => 从 n 种物品中取出 m 个有多少种取法 ( 同种无法区分 ) 计数问题的 DP 定义必须保证不重复计数 这里定义 dp[i+1][j] => 从前 i 种物品中取出 j 个的组合数 根据定义为了从前 i 种物品中取出 j 个,可以从前 i-1 中取出 j-k 个并从 i…

题意:有 n 个客人,m个房间,每个房间可住ci个人,这 n 个人中有 t 对双胞胎,sum{ci}  = n 问你有多少种住房方法. 析:计数DP,dp[i][j] 表示前 i 个房间,还剩下 j 对双胞胎未住,第 i+1 个房间,就从剩下的 j 对双胞胎中选 k 对,然后再从不是双胞胎的人选剩下的,每对先选一个,然后再从剩下的选全部的, 求组合数过程可能要用到逆元,可以提前打表. 代码如下: #pragma comment(linker, "/STACK:1024000000,1024000…

题意:给定一个n*m的矩阵,问你里面有几面积为奇数的正方形. 析:首先能知道的是,大的矩阵是包括小的矩阵的,而且面积为奇数,我们只要考虑恰好在边界上的正方形即可,画几个看看就知道了,如果是3*3的有3个, 5*5有5个,偶数没有,因为面积为奇数.那么结果就有了. 代码如下: #pragma comment(linker, "/STACK:1024000000,1024000000") #include <cstdio> #include <string> #in…

给定一个n*m的网格,求面积为奇数的正方形有多少个. 首先是n*m个面积为1的,然后剩下的要么是边长为奇数,要么被这样一个奇数边长所包围. 原因如下: 对于一个边长不平行于坐标抽的正方形,其边长一定是某个长方形的对角线,而且长方形长宽a,b一定是一奇数,一偶数,这样area = a^2+b^2才是奇数. 所以可以对任何奇数i <= min(n, m) 求出这样的边长正方形以及被包围的正方形个数. 注意对于一个奇数例如5,被包围的正方形可以是以1和4的对角线,2和3的对角线为边,这样对任何一个奇数…

题目链接:点击打开链接 #include <cstdio> #include <vector> using namespace std; typedef long long ll; ll re; vector<int> p; void dfs(int dep, int g) { if (dep == 0) return ; if (p[dep-1] == 1) { re += (dep-1) * (1ll<< (dep-2)); re += g * (1ll…

第一次的增补赛,也是第一场个人排位赛,讲道理打的和屎一样,手速题卡了好久还WA了好多发,难题又切不出来,这种情况是最尴尬的吧! Individual Contest #1: Ploblem D: 题意:给你一个含有N个元素的数组和操作次数m,然后求出经过m次操作后,从区间X到Y的总和:操作如下:{1,6,9}==>{1,7,6,15,9}(多CASE) 题目链接:https://www.codechef.com/problems/CHSPARR 思路: 首先,最容易想到的是单纯的模拟每一次这样的…

A: UVALive 6525 cid=61196#problem/A" style="color:blue; text-decoration:none">Attacking rooks 题解:点击打开链接 C: UVALive 6527 Counting ones 题解:点击打开链接 E: UVALive 6529 Eleven 题解:点击打开链接 F: UVALive 6530 Football 题解:点击打开链接 G: option=com_onlinejudge…

[题目链接] A - Watching TV 模拟.统计一下哪个数字最多即可. #include <bits/stdc++.h> using namespace std; const int maxn = 1e5 + 10; int T, n; char s[maxn]; int a[maxn]; int main() { scanf("%d", &T); while(T --) { scanf("%d", &n); memset(a,…

A - Watching TV /* 题意:求出出现次数最多的数字 */ #include <cstdio> #include <algorithm> #include <cstring> using namespace std; int T,n,a[100010]; char s[110]; int main(){ scanf("%d",&T); while(T--){ memset(a, 0, sizeof(a)); scanf(&quo…

1170 - Counting Perfect BST BST is the acronym for Binary Search Tree. A BST is a tree data structure with the following properties. i)        Each BST contains a root node and the root may have zero, one or two children. Each of the children themsel…

1115. Counting Nodes in a BST (30) 时间限制 400 ms 内存限制 65536 kB 代码长度限制 16000 B 判题程序 Standard 作者 CHEN, Yue A Binary Search Tree (BST) is recursively defined as a binary tree which has the following properties: The left subtree of a node contains only nod…

1115 Counting Nodes in a BST (30 分) A Binary Search Tree (BST) is recursively defined as a binary tree which has the following properties: The left subtree of a node contains only nodes with keys less than or equal to the node's key. The right subtre…

Ant Counting Time Limit : 2000/1000ms (Java/Other)   Memory Limit : 131072/65536K (Java/Other) Total Submission(s) : 3   Accepted Submission(s) : 2 Problem Description Bessie was poking around the ant hill one day watching the ants march to and fro w…

1115 Counting Nodes in a BST (30 分) A Binary Search Tree (BST) is recursively defined as a binary tree which has the following properties: The left subtree of a node contains only nodes with keys less than or equal to the node's key. The right subtre…

1115. Counting Nodes in a BST (30) 时间限制 400 ms 内存限制 65536 kB 代码长度限制 16000 B 判题程序 Standard 作者 CHEN, Yue A Binary Search Tree (BST) is recursively defined as a binary tree which has the following properties: The left subtree of a node contains only nod…

1115 Counting Nodes in a BST(30 分) A Binary Search Tree (BST) is recursively defined as a binary tree which has the following properties: The left subtree of a node contains only nodes with keys less than or equal to the node's key. The right subtree…

Source: PAT A1115 Counting Nodes in a BST (30 分) Description: A Binary Search Tree (BST) is recursively defined as a binary tree which has the following properties: The left subtree of a node contains only nodes with keys less than or equal to the no…

1170 - Counting Perfect BST   PDF (English) Statistics Forum Time Limit: 2 second(s) Memory Limit: 32 MB BST is the acronym for Binary Search Tree. A BST is a tree data structure with the following properties. i)        Each BST contains a root node…

题目:传送门. 题意:t组数据,每组给定n,m,k.有n个格子,m种颜色,要求把每个格子涂上颜色且正好适用k种颜色且相邻的格子颜色不同,求一共有多少种方案,结果对1e9+7取余. 题解: 首先可以将m 与后面的讨论分离.从m 种颜色中取出k 种颜色涂色,取色部分有C(m, k) 种情况: 然后通过尝试可以发现,第一个有k种选择,第二个因不能与第一个相同,只有(k-1) 种选择,第三个也只需与第二个不同,也有(k-1) 种选择.总的情况数为k ×(k-1)^(n-1).但这仅保证了相邻颜色不同,总…

A Binary Search Tree (BST) is recursively defined as a binary tree which has the following properties: The left subtree of a node contains only nodes with keys less than or equal to the node's key. The right subtree of a node contains only nodes with…

A Binary Search Tree (BST) is recursively defined as a binary tree which has the following properties: The left subtree of a node contains only nodes with keys less than or equal to the node's key. The right subtree of a node contains only nodes with…

题意:给出一个序列,构建二叉搜索树(BST),输出二叉搜索树最后两层的节点个数n1和n2,以及他们的和sum: n1 + n2 = sum 递归建树,然后再dfs求出最大层数,接着再dfs计算出最后两层的节点个数,也可以直接一遍dfs,顺便存储各个层的节点数. #include <iostream> #include <cstdio> #include <algorithm> #include <string.h> #define LEFT 1 #defin…

https://pintia.cn/problem-sets/994805342720868352/problems/994805355987451904 A Binary Search Tree (BST) is recursively defined as a binary tree which has the following properties: The left subtree of a node contains only nodes with keys less than or…

题目链接:http://codeforces.com/problemset/problem/893/E 题意: 共q组数据(q <= 10^5),每组数据给定x,y(x,y <= 10^6). 问你有多少种长度为y,乘积为x的整数数列.(可以有负数) 题解: 首先考虑数列只有正整数的情况. 将x分解质因数:x = ∑ a[i]*p[i] 由于x较大,所以要先用线性筛求出素数,再枚举素数分解质因数. 那么一个乘积为x的数列可以看做,将x的所有∑ p[i]个质因子,分配到了y个位置上. 设f(i)…

A Binary Search Tree (BST) is recursively defined as a binary tree which has the following properties: The left subtree of a node contains only nodes with keys less than or equal to the node's key. The right subtree of a node contains only nodes with…

A Binary Search Tree (BST) is recursively defined as a binary tree which has the following properties: The left subtree of a node contains only nodes with keys less than or equal to the node's key. The right subtree of a node contains only nodes with…