问题来源

HDU-1049

问题描述

An inch worm is at the bottom of a well n inches deep. It has enough energy to climb u inches every minute, but then has to rest a minute before climbing again. During the rest, it slips down d inches. The process of climbing and resting then repeats. How long before the worm climbs out of the well? We’ll always count a portion of a minute as a whole minute and if the worm just reaches the top of the well at the end of its climbing, we’ll assume the worm makes it out.

输入

There will be multiple problem instances. Each line will contain 3 positive integers n, u and d. These give the values mentioned in the paragraph above. Furthermore, you may assume d < u and n < 100. A value of n = 0 indicates end of output.

输出

Each input instance should generate a single integer on a line, indicating the number of minutes it takes for the worm to climb out of the well.

例子

AC的代码

#include <iostream>
using namespace std;
int main()
{
	int n, u, d,s,k;
	while (cin >> n >> u >> d)
	{
		if (n == 0)
			break;
		for (s = 0, k = 0; 1;)
		{
			s = u + s;
			k++;
			if (s >= n)
			{
				break;
			}
			s = s - d;
			k++;
		}
		cout << k<<endl;
	}

}

解题思路

s代表位移，k代表时间，当虫上爬后判断是否到达，如果没有则下滑，进行下一循环直到，到达终点。输出时间k。