POJ 1276 Cash Machine DP 难度: 0

题目

http://poj.org/problem?id=1276

题意

一台机器，里面有N种钱，第k种钱币值为Dk，共有Nk张。问不超过cash最多能取出多少钱。

思路

最最简单的可达性dp。

代码

Mem: 384K Time: 329MS

#include <iostream>
#include <cstring>
using namespace std;
const int MAXN = 10;
const int MAXCASH = 1e5 + 1;
int nk[MAXN];
int dk[MAXN];
int n;
int cash;
bool used[MAXCASH];
int dp[MAXCASH];
int dpnum = 0;

int main() {
	while (cin >> cash) {
		memset(used, 0, sizeof(used));
		dpnum = 0;
		cin >> n;
		for (int i = 0; i < n; i++)cin >> nk[i] >> dk[i];
		used[0] = true;
		dp[dpnum++] = 0;
		int ans = 0;
		for (int i = 0; i < n; i++) {
			int dpnow = dpnum;
			for (int j = 0; j < dpnow; j++) {
				int old_status = dp[j];
				for (int k = 1; k <= nk[i] && k * dk[i] + old_status <= cash; k++) {
					int new_status = k * dk[i] + old_status;
					if (!used[new_status]) {
						used[new_status] = true;
						dp[dpnum++] = new_status;
						if(new_status > ans) ans = new_status;
					}
				}
			}
		}
		cout << ans << endl;
	}
	return 0;
}