p70

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LeetCode p70 Climbing Stairs 题解

1.题目：

You are climbing a stair case. It takes n steps to reach to the top.
Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?

题意：

上楼梯问题，输入楼梯层数，你每次可以上一层或者上两层。问有多少种上法。

2.解题思路:

见代码TUT我开始递归超时了。。然后仔细想，其实只要遍历一遍。每次只能上一层或者两层。
所以现在的种数就是上到前一层的种数，加上上到前两层时的种数。这样往后叠加就可以了。

3.代码

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public class Solution {
   

	public int climbStairs(int n) {

		if (n == 1 || n == 2) {
			return n;
		}

		int a = 1;
		int b = 2;
		int c = 0;
		for (int i = 3; i <= n; i++) {
			c = a + b;
			a = b;
			b = c;
		}
		return c;

	}
    
}

4.一些总结：