标签：
Allowance
| Time Limit: 1000MS |
|
Memory Limit: 65536K |
| Total Submissions: 3008 |
|
Accepted: 1218 |
Description
As a reward for record milk production, Farmer John has decided to start paying Bessie the cow a small weekly allowance. FJ has a set of coins in N (1 <= N <= 20) different denominations, where each denomination of coin evenly divides the next-larger denomination (e.g., 1 cent coins, 5 cent coins, 10 cent coins, and 50 cent coins).Using the given set of coins, he would like to pay Bessie at least some given amount of money C (1 <= C <= 100,000,000) every week.Please help him ompute the maximum number of weeks he can pay Bessie.
Input
* Line 1: Two space-separated integers: N and C
* Lines 2..N+1: Each line corresponds to a denomination of coin and contains two integers: the value V (1 <= V <= 100,000,000) of the denomination, and the number of coins B (1 <= B <= 1,000,000) of this denomation in Farmer John‘s possession.
Output
* Line 1: A single integer that is the number of weeks Farmer John can pay Bessie at least C allowance
Sample Input
3 6
10 1
1 100
5 120
Sample Output
111
Hint
INPUT DETAILS:
FJ would like to pay Bessie 6 cents per week. He has 100 1-cent coins,120 5-cent coins, and 1 10-cent coin.
OUTPUT DETAILS:
FJ can overpay Bessie with the one 10-cent coin for 1 week, then pay Bessie two 5-cent coins for 10 weeks and then pay Bessie one 1-cent coin and one 5-cent coin for 100 weeks.
题意：有各种面值的钞票，每种都有若干张，每个星期都要用这些钞票的一部分去支付C元及以上的费用，最终要使得支付的星期尽可能的多，那么最多可以支付多少星期
思路：首先按面值从大到小来排序，若钞票的面值大于等于C，只能一张一张先付掉，之后只剩下比C小的钞票，这些钞票进行各种组合使得sum大于C，具体组合方法：
先按面值从大到小循环，用一个数组来记录各种各种面值的钞票各用了多少张，使得总和sum尽可能接近C且比C小一点；第二步：按面值从小到大循环，继续用上面所述数组来记录各种面值的钞票还需要用多少张，最终使得总和sum超过C，但最多只能超过一点点。
组合出sum之后，看看这种组合最多能有几组。之后再进行下一次新的组合……直到所有的组合都用完了，结束。
AC代码：
#define _CRT_SECURE_NO_DEPRECATE
#include<iostream>
#include<algorithm>
using namespace std;
const int V_MAX = 20;
struct money {
int V;
int num;
bool operator <(const money&b) {
return V > b.V;
}
};
money mon[V_MAX];
int need[V_MAX];
int main() {
int N, C;
while (cin >> N >> C) {
int week = 0;
for (int i = 0;i < N;i++) {
scanf("%d%d", &mon[i].V, &mon[i].num);
if (mon[i].V >= C) {
week += mon[i].num;//面值大于C的钱只能一张一星期的给
mon[i].num = 0;
}
}
sort(mon,mon+N);//按面值从大到小排
while (1) {//每一次循环将产生一种能超过sum的钞票组合
int sum = C;//每一种组合要凑足sum
memset(need, 0, sizeof(need));
for (int i = 0;i < N;i++) {//面值从大到小
if(sum > 0&&mon[i].num) {
int can_use = min(mon[i].num,sum/mon[i].V);//当前面值的钞票的最多能拿几张，尽量多，但不能超过sum
if (can_use>0) {
sum -= can_use*mon[i].V;
need[i] = can_use;
}
}
}
for (int i = N - 1;i >= 0;i--) {//面值从小到大
if (sum > 0 && mon[i].num) {
int can_use = min(mon[i].num-need[i],(sum+mon[i].V-1)/mon[i].V);//当前面值的钞票尽量多拿，但超过sum一点点就可以了，不要浪费
if (can_use>0) {
sum -= can_use*mon[i].V;
need[i] += can_use;
}
}
}
if (sum > 0) {
break;
}
//至此拼凑出sum需要各种面值的钞票的数量已经都存放在need[]数组中了
int add = INT_MAX;
for (int i = 0;i < N;i++) {
if (need[i] == 0)continue;
add= min(add, mon[i].num / need[i]);//当前的拼凑出sum的组合最多能有几组
}
week += add;
for (int i = 0;i < N;i++) {//将该组合所使用掉的钞票去除
if (need[i] == 0)continue;
mon[i].num -= need[i] * add;
}
}
cout << week << endl;
}
return 0;
}
poj 3040 Allowance
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原文地址：http://www.cnblogs.com/ZefengYao/p/5835505.html
