爬楼梯的问题Climbing Stairs

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?

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//类似于斐波那契数列public class Solution {    public int climbStairs(int n) {         if(n <= 0) return 0;    if(n == 1) return 1;    if(n == 2) return 2;    int one_step_before = 2;    int two_steps_before = 1;    int all_ways = 0;    for(int i=2; i<n; i++){        all_ways = one_step_before + two_steps_before;        two_steps_before = one_step_before;        one_step_before = all_ways;    }    return all_ways;    }}