Two

Two

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题意：给出a,b两个字符串，问他们不必连续的字串中有多少对相同。
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解法：dp。f[i]表示对于b串当前读到的数字匹配到a串的第i个位置一共有的次数。
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#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
using namespace std;

const int maxn = 2000;
const int mo = 1000000007;
int a[maxn], f[maxn], n, m, sum, x, add, ans;

int main() {

    while ((scanf("%d %d", &n, &m)) != EOF) {
        for (int i = 1; i <= n; i++) scanf("%d", &a[i]);
        memset(f, 0, sizeof(f));
        for (int j = 1; j <= m; j++) {
            scanf("%d", &x);
            sum = 0;
            for (int i = 1; i <= n; i++) {
                add = 0;
                if (a[i] == x) add = sum+1;
                sum = (sum+f[i])%mo;
                f[i] = (f[i]+add)%mo;
            }
        }
        ans = 0;
        for (int i = 1; i <= n; i++) ans = (ans+f[i])%mo;
        printf("%d\n", ans);
    }
}