HDU2639[背包第K大]

题目链接【http://acm.hdu.edu.cn/showproblem.php?pid=2639】

题意：求第k大背包。

题解：利用二路归并的思想，求解第K大的值。

#include<bits/stdc++.h>
using namespace std;
typedef long long LL;
const int MAXN = 1050;
int dp[MAXN][35], w[MAXN], v[MAXN];
int N, W, K;
int A[35], B[35];
void super_kth()
{
    for(int i = 1; i <= N; i++)
    {
        for(int j = W; j >= w[i]; j--)
        {
            for(int l = 1; l <= K; l++)
            {
                A[l] = dp[j - w[i]][l] + v[i]; //放i
                B[l] = dp[j][l];//不放i
            }
            int nu = 1, x = 1, y = 1;
            A[K + 1] = -1;
            B[K + 1] = -1;
            while(nu <= K && (A[x] != -1 || B[y] != -1))
            {
                if(A[x] > B[y])
                    dp[j][nu] = A[x++];
                else
                    dp[j][nu] = B[y++];
                if(dp[j][nu] != dp[j][nu - 1])//不相等的第k大背包
                    nu++;
            }
        }
    }
    printf("%d
", dp[W][K]);
}
int main ()
{
    int T;
    scanf("%d", &T);
    while(T--)
    {
        memset(dp, 0, sizeof(dp));
        scanf("%d%d%d", &N, &W, &K);
        for(int i = 1; i <= N; i++)
            scanf("%d", &v[i]);
        for(int i = 1; i <= N; i++)
            scanf("%d", &w[i]);
        super_kth();
    }
    return 0;
}