Seek the Name, Seek the Fame

POJ

题意:给定若干个长度小于等于(400000)的字符串,在每个字符串中求出既是前缀又是后缀的子串长度.

分析:字符串哈希记录前缀值,然后直接枚举长度,分别表示出前缀和后缀的哈希值,并判断是否相等即可.

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
#include<cmath>
#include<queue>
#include<map>
#include<set>
#define ll long long
#define ull long long
using namespace std;
const int N=400005;
char s[N];int p=1e9+7;
ull sum[N],Base[N];
int main(){
	Base[0]=1;for(int i=1;i<N;++i)Base[i]=Base[i-1]*p;
	while(~scanf("%s",s+1)){
		int n=strlen(s+1);
		for(int i=1;i<=n;++i)
			sum[i]=sum[i-1]*p+(ull)s[i]-'a'+1;
		for(int i=1;i<=n;++i){
			if(sum[i]==sum[n]-sum[n-i]*Base[i])printf("%d ",i);
		}
		printf("
");
	}
    return 0;
}