From www.hankcs.com/program/cpp/poj-3040-allowance.html

POJ/3040_hankcs.cpp

@@ -0,0 +1,102 @@
+#include <iostream>
+#include <functional>
+#include <algorithm>
+#include <limits>
+using namespace std;
+ 
+typedef pair<int, int> Coin;	// 硬币 面值和数量
+Coin coin[20];
+int need[20];
+ 
+///////////////////////////SubMain//////////////////////////////////
+int main(int argc, char *argv[])
+{
+#ifndef ONLINE_JUDGE
+    freopen("in.txt", "r", stdin);
+    freopen("out.txt", "w", stdout);
+#endif
+	int N, C;
+	cin >> N >> C;
+	for (int i = 0; i < N; ++i)
+	{
+		cin >> coin[i].first >> coin[i].second;
+	}
+	int week = 0;
+	// 面额不小于C的一定可以支付一周
+	for (int i = 0; i < N; ++i)
+	{
+		if (coin[i].first >= C)
+		{
+			week += coin[i].second;
+			coin[i].second = 0;
+		}
+	}
+	sort(coin, coin + N, greater<Coin>());
+	while(true)
+	{
+		int sum = C; // 等待凑足的sum
+		memset(need, 0, sizeof(need));
+		// 从大到小
+		for (int i = 0; i < N; ++i)
+		{
+			if (sum > 0 && coin[i].second > 0)
+			{
+				int can_use = min(coin[i].second, 
+								  sum / coin[i].first);
+				if (can_use > 0)
+				{
+					sum -= can_use * coin[i].first;
+					need[i] = can_use;
+				}
+			}
+		}
+		// 从小到大
+		for (int i = N - 1; i >= 0; --i)
+		{
+			if (sum > 0 && coin[i].second > 0)
+			{
+				int can_use = min(coin[i].second - need[i],                   // 上个loop用掉了一些
+								  (sum + coin[i].first - 1) / coin[i].first); // 允许多出不超过一个面值的金额
+				if (can_use > 0)
+				{
+					sum -= can_use * coin[i].first;
+					need[i] += can_use;
+				}
+			}
+		}
+ 
+		if(sum > 0)
+		{
+			break;
+		}
+ 
+		int add_up = numeric_limits<int>::max(); // 凑起来的week数
+		// add_up多少个最优的week 受限于 每种面值能满足最优解下的需求个数多少次
+		for (int i = 0; i < N; ++i)
+		{
+			if (need[i] == 0)
+			{
+				continue;
+			}
+			add_up = min(add_up, coin[i].second / need[i]);
+		}
+		week += add_up;
+		// 最优解生效，更新剩余硬币数量
+		for (int i = 0; i < N; ++i)
+		{
+			if (need[i] == 0)
+			{
+				continue;
+			}
+			coin[i].second -= add_up * need[i];
+		}
+	}
+	cout << week << endl;
+#ifndef ONLINE_JUDGE
+    fclose(stdin);
+    fclose(stdout);
+    system("out.txt");
+#endif
+    return 0;
+}
+///////////////////////////End Sub//////////////////////////////////