POJ 1276-Cash Machine（多重部分和-dp）

A Bank plans to install a machine for cash withdrawal. The machine is able to deliver appropriate @ bills for a requested cash amount. The machine uses exactly N distinct bill denominations, say Dk, k=1,N, and for each denomination Dk the machine has a supply of nk bills. For example, 

N=3, n1=10, D1=100, n2=4, D2=50, n3=5, D3=10 

means the machine has a supply of 10 bills of @100 each, 4 bills of @50 each, and 5 bills of @10 each. 

Call cash the requested amount of cash the machine should deliver and write a program that computes the maximum amount of cash less than or equal to cash that can be effectively delivered according to the available bill supply of the machine. 

Notes: 
@ is the symbol of the currency delivered by the machine. For instance, @ may stand for dollar, euro, pound etc. 

The program input is from standard input. Each data set in the input stands for a particular transaction and has the format: 

cash N n1 D1 n2 D2 ... nN DN 

where 0 <= cash <= 100000 is the amount of cash requested, 0 <=N <= 10 is the number of bill denominations and 0 <= nk <= 1000 is the number of available bills for the Dk denomination, 1 <= Dk <= 1000, k=1,N. White spaces can occur freely between the numbers in the input. The input data are correct. 

For each set of data the program prints the result to the standard output on a separate line as shown in the examples below. 

735 3  4 125  6 5  3 350
633 4  500 30  6 100  1 5  0 1
735 0
0 3  10 100  10 50  10 10

735
630
0
0

The first data set designates a transaction where the amount of cash requested is @735. The machine contains 3 bill denominations: 4 bills of @125, 6 bills of @5, and 3 bills of @350. The machine can deliver the exact amount of requested cash. 

In the second case the bill supply of the machine does not fit the exact amount of cash requested. The maximum cash that can be delivered is @630. Notice that there can be several possibilities to combine the bills in the machine for matching the delivered cash. 

In the third case the machine is empty and no cash is delivered. In the fourth case the amount of cash requested is @0 and, therefore, the machine delivers no cash.

Southeastern Europe 2002

現金cash元，有N種零錢，依次給出數量及其面值。求出用這些零錢能夠換零的不超過cash的最大金額。

多重部分和的模板，dp[i]儲存的是能否得到金額i，不小於零時表示能夠得到。然後從cash往下列舉dp陣列，一旦滿足就輸出i。

因為用二維dp陣列過大，所以使用一維重複利用。

#include<iostream>
#include<cstdio>
#include<iomanip>
#include<cmath>
#include<cstdlib>
#include<cstring>
#include<map>
#include<algorithm>
using namespace std;
#define INF 0xfffffff
#define MAXN 100005
int a[MAXN],m[MAXN];
int cash,n;
void init()
{
    memset(dp,-1,sizeof(dp));
    memset(a,0,sizeof(a));
    memset(m,0,sizeof(m));
}
int dp[MAXN];

void solve()
{
    dp[0]=0;
    int i,j;
    for(i=0; i<n; ++i)
        for(j=0; j<=cash; ++j)
        {
            if(dp[j]>=0) dp[j]=m[i];
            else if(j<a[i]||dp[j-a[i]]<=0) dp[j]=-1;
            else dp[j]=dp[j-a[i]]-1;
        }
    for(int i=cash; i>=0; --i)//從cash往下列舉
        if(dp[i]>=0)
        {
            cout<<i<<endl;
            break;
        }
}

int main()
{
#ifdef ONLINE_JUDGE
#else
    freopen("F:/cb/read.txt","r",stdin);
    //freopen("F:/cb/out.txt","w",stdout);
#endif
    while(~scanf("%d%d",&cash,&n))
    {
        init();
        for(int i=0; i<n; ++i)
            cin>>m[i]>>a[i];
        solve();
    }
    return 0;
}
/*
735 3  4 125  6 5  3 350
633 4  500 30  6 100  1 5  0 1
735 0
0 3  10 100  10 50  10 10
*/