1114 Piggy-Bank - 完全背包 恰好达到状态最小价值

http://acm.hdu.edu.cn/showproblem.php?pid=1114 Piggy-Bank

#include <cmath>
#include <string>
#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;
#define CLR(c,v) (memset(c,v,sizeof(c)))

template <typename _T>
_T Max(_T a,_T b){
	return a<b?b:a;
}
template <typename _T>
_T Max(_T a,_T b,_T c){
	return a<Max(b,c)?Max(b,c):a;
}
template <typename _T>
_T Min(_T a,_T b){
	return a>b?b:a;
}
template <typename _T>
_T Min(_T a,_T b,_T c){
	return a>Min(b,c)?Min(b,c):a;
}

const int inf = -(1<<30);
const int INF =  (1<<30);
const int M   =  1e6 + 10;

int max_cost;
int dp[M];

int main()
{
	//freopen("in.txt","r",stdin);
	int Ncase;
	cin >> Ncase;
	while(Ncase--){
		int empty_box, max_weight , n;
		cin >> empty_box >> max_weight >> n;
		max_cost = max_weight - empty_box;
		CLR(dp,-1);
		for(int i = 0 ; i <= max_cost ; i++)
			dp[i] = INF;

		dp[0] = 0;
		int ans = INF;
		for(int i = 1; i <= n ; i++){
			int cost,value;
			cin >> value >> cost;
			for(int j = cost ; j <= max_cost ; j++){
				if(dp[j-cost] != -1 )
					dp[j] = Min(dp[j],dp[j-cost]+value);
			}
			if(dp[max_cost] != -1)
				ans = Min(dp[max_cost],ans);
		}
		if(ans == INF)
			printf("This is impossible.\n");
		else
			printf("The minimum amount of money in the piggy-bank is %d.\n",ans);
	}
	return 0;
}