cf519D. A and B and Interesting Substrings(前缀和)

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cf519D. A and B and Interesting Substrings(前缀和)

题意给出$26$个字母对应的权值和一个字符串问满足以下条件的子串有多少首尾字母相同中间字母权值相加为0 Sol 我们要找到区间满足$sum[i] - sum[j] = 0$ $sum[i] = sum[j]$ 开$26$个map维护一下$sum$相等的子串就可以 /* */ #include<iostream> #include<cstdio> #include<cstring> #include<algorithm> #include<map…

cf519D . A and B and Interesting Substrings 数据结构map

题意: 已知26个小写字母有各自的权值(正,负,或0) 现在给出一个字符串,长度<=1e5 问这个字符串有多少个子串满足: 开头的字母和结尾的字母一样字符串除了开头和结尾的字母外,其余的字母的权值和为0 本来是一道水题,一看就知道大体的思路了,结果硬是搞了一个多小时先是用set,发现超时了,改为用map 思路: 1.我们先预处理这个字符串的权值的前缀和 sum[i]表示从字符串的起点到i的权值和 2.我们要找到的子串,设以l开头和r结尾,则有 str[r] == str[l] 和 sum[r…

Codeforces Round #294 (Div. 2) D. A and B and Interesting Substrings [dp 前缀和 ]

传送门 D. A and B and Interesting Substrings time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output A and B are preparing themselves for programming contests. After several years of doing sports pro…

[CF Round #294 div2] D. A and B and Interesting Substrings 【Map】

题目链接:D. A and B and Interesting Substrings 题目大意给定26个小写字母的权值,一共26个整数(有正有负). 给定一个小写字母组成的字符串(长度10^5),求有多少长度大于1的子串满足: 1)首尾字符相同. 2)除了首尾字符外,其他字符的权值和为0. 题目分析使用STL Map.开26个Map,给每个字母开一个. 先求出权值的前缀和 Sum[] . 然后1到l枚举每一位字符,如果是a,那么 Ans += Map[a][Sum[i - 1]]; 然后 +…

CF519 ABCD D. A and B and Interesting Substrings(map,好题）

A:http://codeforces.com/problemset/problem/519/A 水题没什么好说的. #include <iostream> #include <string.h> #include <stdio.h> #include <math.h> #include <algorithm> #include <queue> #define inf 0x3f3f3f3f using namespace std; ]…

Codeforces Round #294 (Div. 2)D - A and B and Interesting Substrings 字符串

D. A and B and Interesting Substrings time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output A and B are preparing themselves for programming contests. After several years of doing sports program…