2016 Multi-University Training Contest 5 1011 Two DP

 http://acm.hdu.edu.cn/showproblem.php?pid=5791

HDU5791 Two

题意 ：两个数组，多少个不连续子串相等

思路：

dp[i][j] ：a串i结尾，b串j结尾的不连续子串数目个数

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<iostream>
using namespace std;
typedef long long ll;
const int maxn=1e3+7;
const int mod=1e9+7;
const int inf=0x3f3f3f3f;
ll dp[maxn][maxn],a[maxn],b[maxn];
int n,m;
int main(){
    while(~scanf("%d%d",&n,&m)){
        for(int i=1;i<=n;i++)scanf("%lld",&a[i]);
        for(int i=1;i<=m;i++)scanf("%lld",&b[i]);
        memset(dp,0,sizeof(dp));
        for(int i=1;i<=n;i++){
            for(int j=1;j<=m;j++){
                dp[i][j]=(dp[i-1][j]+dp[i][j-1]-dp[i-1][j-1]+(a[i]==b[j]?dp[i-1][j-1]+1:0)+mod)%mod;
            }
        }
        printf("%lld\n",dp[n][m]);
    }
    return 0;
}