HDU 1171 Big Event in HDU【多重背包】

大意：有n个物品，告诉你每个物品的价值问能否分成价值a、b两份使{a > b  && a + b == 总价值  && a - b尽量小}

分析：多重背包

代码：

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;

const int maxn = 55;
const int INF = 1000000000;

int n, sum;
int vo[maxn * maxn * 100];
int dp[maxn * maxn];
int solve() {
    memset(dp, 0, sizeof(dp));
    for(int i = 1; i < n; i++) {
        for(int j = sum; j >= vo[i]; j--) {
            dp[j] = max(dp[j], dp[j - vo[i]] + vo[i]);
        }
    }
    int mid = (sum + 1) >> 1;
    int i;
    for(i = mid; i <= sum; i++) {
        if(dp[i] == i) break;
    }
    return i;
}

int main() {
    int m;
    int a, b;
    while(scanf("%d",&m) ) {
        if(m < 0) break;
        n = 1;
        sum = 0;
        for(int i = 1; i <= m; i++) {
            scanf("%d %d",&a, &b);
            sum += a * b;
            for(int k = 1; k <= b; k *= 2) {
                vo[n++] = k * a;
                b -= k;
            }
            if(b) vo[n++] = b * a;
        }
        int ans = solve();
        printf("%d %d
",ans, sum - ans);
    }
    return 0;
}