一些dp

 for(int i=1; i<=n; i++){
        for(int j=weight[i]; j<=V; j++){
            dp[i][j] = max(dp[i][j], dp[i-1][j-weight[i]]+value[i]);
        }
 }



 int now=1, pre = 0;
 for(int i=1; i<=n; i++){
    for(int j=weight[i]; j<=V; j++){
        dp[now][j] = max(dp[now][j], dp[pre][j-weight[i]]+value[i]);
    }
    //,,,,
 }

 for(int i=1; i<=n; i++){
    for(int j=V; j>=weight; j--){
        dp[j] = max(dp[j], dp[j-weight[i]]+value[i]);
    }
 }