HDU - 1085 Holding Bin-Laden Captive!（硬币问题）

题目：

Description

We all know that Bin-Laden is a notorious terrorist, and he has disappeared for a long time. But recently, it is reported that he hides in Hang Zhou of China! 
“Oh, God! How terrible! ” 



Don’t be so afraid, guys. Although he hides in a cave of Hang Zhou, he dares not to go out. Laden is so bored recent years that he fling himself into some math problems, and he said that if anyone can solve his problem, he will give himself up! 
Ha-ha! Obviously, Laden is too proud of his intelligence! But, what is his problem? 
“Given some Chinese Coins (硬币) (three kinds-- 1, 2, 5), and their number is num_1, num_2 and num_5 respectively, please output the minimum value that you cannot pay with given coins.” 
You, super ACMer, should solve the problem easily, and don’t forget to take $25000000 from Bush! 

Input

Input contains multiple test cases. Each test case contains 3 positive integers num_1, num_2 and num_5 (0<=num_i<=1000). A test case containing 0 0 0 terminates the input and this test case is not to be processed. 

Output

Output the minimum positive value that one cannot pay with given coins, one line for one case. 

Sample Input

1 1 30 0 0

Sample Output

4

母函数方法：

#include<iostream>using namespace std;int main(){int s[8001], n1, n2, n5, l[6] = { 0, 1, 2, 3, 4, 5 };while (cin >> n1 >> n2 >> n5){if (n1 + n2 + n5 == 0)break;for (int i = 0; i <= 8000; i++)s[i] = 0;for (int i = 0; i <= n1; i++)s[i] = 1;for (int i = 8000; i > 0; i--)for (int j = 2; j <= i&&j <= n2 * 2; j += 1)s[i] += s[i - j];for (int i = 8000; i > 0; i--)for (int j = 5; j <= i&&j <= n5 * 5; j += 1)s[i] += s[i - j];bool flag = true;for (int i = 0; i <= 8000 && flag; i++){if (s[i] == 0){cout << i << endl;flag = false;}}if (flag)cout << 8001 << endl;}return 0;}

然而超时了。

针对本题的方法：

#include<iostream>using namespace std;int f(int n1, int n2, int n5){if (n1 == 0)return 1;int key = n2 * 2 + n1 + 1;if (key < 5)return key;return n5 * 5 + key;}int main(){int n1, n2, n5;while (cin >> n1 >> n2 >> n5){if (n1 + n2 + n5 == 0)break;cout << f(n1, n2, n5) << endl;}return 0;}