ZOJ 2059 The Twin Towers

双塔DP。

dp[i][j]表示前i个物品，分成两堆（可以不全用），价值之差为j的时候，较小一堆的价值为dp[i][j]。

#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
using namespace std;

int dp[][ + ];
int a[];
int n, sum;

void read()
{
    for (int i = ; i <= n; i++) scanf("%d", &a[i]);
}

void work()
{
    sum = ;
    for (int i = ; i <= n; i++) sum = sum + a[i];
    memset(dp, -, sizeof dp);
    int h; h = a[];
    dp[][h + sum] = dp[][ - h + sum] = dp[][sum] = ;
    for (int i = ; i <= n; i++)
    {
        h = a[i];
        for (int j = ; j <= sum*; j++) dp[i][j] = dp[i - ][j];
        for (int j = ; j <= sum*; j++)
        {
            if (dp[i - ][j] == -) continue;

            int tmp = j - sum;
            if (tmp >= )
            {
                dp[i][h + tmp + sum] = max(dp[i][h + tmp + sum], dp[i - ][j]);
                dp[i][tmp - h + sum] = max(dp[i][tmp - h + sum], dp[i - ][j] + min(tmp, h));
            }
            else if (tmp<)
            {
                tmp = -tmp;
                dp[i][ - (tmp + h) + sum] = max(dp[i][ - (tmp + h) + sum], dp[i - ][j]);
                dp[i][h - tmp + sum] = max(dp[i][h - tmp + sum], dp[i - ][j] + min(tmp, h));
            }
        }
    }
    int ans = ;
    for (int i = ; i <= n; i++) ans = max(ans, dp[i][sum]);
    if (ans == ) printf("Sorry\n");
    else printf("%d\n", ans);
}

int main()
{
    while (~scanf("%d", &n))
    {
        read();
        if (n < ) break;
        if (n <=) printf("Sorry\n");
        else work();
    }
    return ;
}