标签:codeforces dp
给出两个字符串,问第一个字符串由多少种方法提取出一些子串使这些子串中都包含t模式串。
#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
#define MAX 100007
using namespace std;
char s[MAX],t[MAX];
int mark[MAX];
const int mod = 1e9+7;
int dp[MAX];
int sum[MAX];
void get_next ( char p[] , int next [] )
{
int i = 0 , k = -1 , len = strlen ( p );
next[0] = -1;
while ( i < len )
if ( k == -1 || p[i] == p[k] )
i++,k++,next[i]=k;
else k = next[k];
}
void match ( char s[] , char p[] )
{
memset ( mark , 0 , sizeof ( mark ) );
int next[MAX];
get_next ( p , next );
int len1 = strlen ( s );
int len2 = strlen ( p );
int i = 0 , j = 0;
while (i < len1 )
{
if ( j == -1 || s[i] == p[j] ) i++ , j++;
else j = next[j];
if ( j == len2 )
mark[i] = i-len2+1;
}
}
int main ( )
{
while ( ~scanf ( "%s" , s ) )
{
scanf ( "%s" , t );
match ( s , t );
sum[0] = dp[0] = 0;
int n = strlen ( s );
for ( int i = 1 ; i <= n ; i++ )
if ( !mark[i] )
mark[i] = mark[i-1];
for ( int i = 1 ; i <= n ; i++ )
{
dp[i] = dp[i-1];
int l = mark[i];
if ( !l ) continue;
dp[i] += (sum[l-1]+l)%mod;
dp[i] %= mod;
sum[i] = sum[i-1] + dp[i];
sum[i] %= mod;
}
printf ( "%d\n" , dp[n] );
}
}
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codeforces 494B B. Obsessive String(dp)
标签:codeforces dp
原文地址:http://blog.csdn.net/qq_24451605/article/details/48947325