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);    }}