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[Leetcode] 70. Climbing Stairs Java

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?

Note: Given n will be a positive integer.

 

题意及分析:有一个n步长的梯子,每次只能爬一步或者两步,求从爬完梯子一共有多少种走法。动态规划的题目,因为到第i步只有两种方法(要么从i-2爬两步或者从i-1爬一步),所以走到第i步的d(i)=d(i-1)+d(i-1),即到i-1步的走法加上到第i-2的走法。所以遍历到第n步就可以求出解了。

 

代码:

public class Solution {

	public int climbStairs(int n) {
		int[] A=new int[n]; //用来记录到每一步有多少种走法
		A[0]=1;
		if(n==1)
			return 1;
		A[1]=2;
		for(int i=2;i<n;i++){
			A[i]=A[i-1]+A[i-2];
		}
		return A[n-1];
	}
}

  

 

[Leetcode] 70. Climbing Stairs Java