哎,最近都在做图论,没有练DP,现在一遇到DP就不会了= =
因为有合并这个操作,所以只要是首位相同的字符串肯定是能够构成good串的,那么只要统计在奇数位上出现的0,1的个数和偶数位数,随便递推一下就出来了
#include <cstdio> #include <cstring> #include <cmath> #include <algorithm> #include <climits> #include <string> #include <iostream> #include <map> #include <cstdlib> #include <list> #include <set> #include <queue> #include <stack> using namespace std; typedef long long LL; const int maxn = 100005; LL cntodd[2],cnteven[2]; char buf[maxn]; int main() { scanf("%s",buf + 1); int len = strlen(buf + 1); LL sumodd = 0,sumeven = 0; for(int i = 1;i <= len;i++) { int now = buf[i] - ‘a‘; if(i & 1) cntodd[now]++; else cnteven[now]++; if(i & 1) { sumodd += cntodd[now]; sumeven += cnteven[now]; } else { sumodd += cnteven[now]; sumeven += cntodd[now]; } } cout << sumeven << " " << sumodd << endl; return 0; }
CodeForces 451D Count Good Substrings,布布扣,bubuko.com
时间: 2024-10-10 11:13:41