hdu 1171 Big Event in HDU

题目意思是有多种物品，每种物品的价值不确定，数量也不确定，很明显就是背包问题，…………

//深搜加剪枝

//深搜代码：
#include <iostream>
#include <cstdio>
using namespace std;
int v[55], m[55], h[53], N, B, res;
bool flag;
void dfs(int n, int sum){
    if(flag) return;
    if(sum > res) res = sum;
    if(res == B){
        flag = true;
        return;
    }
    if(n == N) return;
    //后缀数组优化，剪枝
    if(sum + h[n] <= res) return;
    else if(sum + h[n] <= B){
        res = sum + h[n];
        if(res == B) flag = true;
        return ;
    }
    for(int i = 0; sum + v[n] * i <= B && i <= m[n]; ++i){
        dfs(n + 1, sum + v[n] * i);
    }
}

int main()
{
    int i, k, s;
    while(scanf("%d", &N) != EOF){
        if(N <= 0) break;
        s = 0;
        for(i = 0; i < N; ++i){
            scanf("%d%d", &v[i], &m[i]);
            h[i] = v[i] * m[i];
            s += h[i];
        }
        for(k = N - 2; k >= 0; --k) h[k] += h[k+1];
        B = s / 2; res = 0; flag = false;
        dfs(0, 0);
        printf("%d %d
", s - res, res);
    }
    return 0;
}

//DP代码（一定的物品可以达到价值的标记为true,然后从中间值搜索）

//DP代码：
#include<stdio.h>
#include<string.h>
#define N 2500000
bool a[N], b[N];
int main(){
    int n, sum, V[53], M[53];
    while(scanf("%d", &n) != EOF){
        if(n < 0) break;
        sum = 0;
        for(int i = 1; i <= n; ++i){
            scanf("%d%d", &V[i], &M[i]);
            sum += V[i] * M[i];
        }
        memset(a, false, sizeof(a));
        memset(b, false, sizeof(b));
        for(int i = 0; i <= V[1]*M[1]; i += V[1]) a[i] = true;
        int value = V[1] * M[1];
        for(int i = 2; i <= n; ++i){
            for(int j = 0; j <= value; ++j)
                for(int k = 0; k <= V[i] * M[i]; k += V[i])
                    b[j + k] += a[j];
            value += V[i] * M[i];
            for(int j = 0; j <= value; ++j){
                a[j] = b[j]; b[j] = 0;
            }
        }
        for(value = sum / 2; a[value] == 0; --value) ;
        printf("%d %d
", sum - value, value);
    }
    return 0;
}