dp[0]=a[0];
for(int i=1; i<n; i++){　　if(dp[i-1]>0)　　　　dp[i]=dp[i-1]+a[i];　　else       dp[i]=a[i];
}

#include <iostream>#include<cstdio>#include <cstring>#include <algorithm>using namespace std;const int MAX=1000;int dp[MAX][MAX]={0};int LCS( char *X, char *Y, int m, int n ){    for (int i=1; i<=m; i++)    {        for (int j=1; j<=n; j++)        {            if (X[i-1] == Y[j-1])                dp[i][j] = dp[i-1][j-1] + 1;            else                dp[i][j] = max(dp[i-1][j], dp[i][j-1]);        }    }    return dp[m][n];}