hdu 5791 two 多校联赛第五场

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Two

Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 65536/65536 K (Java/Others)
Total Submission(s): 986 Accepted Submission(s): 453

Problem Description

Alice gets two sequences A and B. A easy problem comes. How many pair of sequence A' and sequence B' are same. For example, {1,2} and {1,2} are same. {1,2,4} and {1,4,2} are not same. A' is a subsequence of A. B' is a subsequence of B. The subsequnce can be not continuous. For example, {1,1,2} has 7 subsequences {1},{1},{2},{1,1},{1,2},{1,2},{1,1,2}. The answer can be very large. Output the answer mod 1000000007.

Input

The input contains multiple test cases.

For each test case, the first line cantains two integers

N,M(1≤N,M≤1000). The next line contains N integers. The next line followed M integers. All integers are between 1 and 1000.

Output

For each test case, output the answer mod 1000000007.

Sample Input

3 21 2 32 13 21 2 31 2

Sample Output

Author

ZSTU

Source

2016 Multi-University Training Contest 5

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题解

等于所有圆圈相加总和

dp[i][j]表示A序列前i个数和B序列前j个数的相同子序列对有多少个。复杂度 $O(n^2)$

#include<stdio.h>#include<iostream>#include<algorithm>#include<string.h>const int INF=1000000007;using namespace std;int n,m;int a[1005];int b[1005];int dp[1005][1005];int main(){   while(scanf("%d%d",&n,&m)!=EOF)   {       for(int i=1;i<=n;i++)        scanf("%d",&a[i]);       for(int i=1;i<=m;i++)        scanf("%d",&b[i]);        memset(dp,0,sizeof(dp));       for(int i=1;i<=n;i++)       {           for(int j=1;j<=m;j++)           {               if(a[i]==b[j])               {                   dp[i][j]=(dp[i-1][j]+dp[i][j-1]+1)%INF;               }               else               {                   dp[i][j]=(dp[i-1][j]+dp[i][j-1]-dp[i-1][j-1])%INF;               }           }       }       for(int i=1;i<=n;i++)       {           for(int j=1;j<=m;j++)            printf("%d ",dp[i][j]);           printf("\n");       }      if(dp[n][m]<0)        printf("%d\n",dp[n][m]+INF);      else        printf("%d\n",dp[n][m]);   }   return 0;}

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