题目链接:点击打开链接
题意:
杭电分设备;
有 n 种设备;
每种都不同,每种都有 w[i] 个;
问怎样分才能使分成的两堆之差最少;
理解:
多重背包;
套模板;
递推式:dp[i] = max(dp[i], dp[i - mul * v[i]] + mul * v[i]);
其中的值根据代码定义;
也可以 01背包做;
但是顺手就用了多重背包;
有个坑,输入结束标志是一个负数,而不是-1;
代码如下:
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <ctime>
#include <iostream>
#include <algorithm>
#include <vector>
#include <string>
#include <map>
#include <set>
#include <queue>
#include <stack>
using namespace std;
typedef long long LL;
typedef pair<int, int> PII;
const int MIN_INF = 1e-7;
const int MAX_INF = (1e9) + 7;
#define X first
#define Y second
int dp[555555];
int v[1111];
int w[1111];
int main() {
int n;
while (cin >> n && n >= 0) {
memset(dp, 0, sizeof(dp));
int sum = 0;
for (int i = 0; i < n; ++i) {
cin >> v[i] >> w[i];
sum += v[i] * w[i];
}
for (int i = 0; i < n; ++i) {
int num = w[i];
for (int k = 1; num > 0; k <<= 1) { // 注意是左移等于
int mul = min(k, num);
for (int j = sum / 2; j >= mul * v[i]; --j) {
dp[j] = max(dp[j], dp[j - mul * v[i]] + mul * v[i]);
}
num -= k;
}
}
cout << sum - dp[sum / 2] << " ";
cout << dp[sum / 2] << endl;
}
return 0;
}