LeetCode-Easy刷題(16) 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?

Note: Given n will be a positive integer.

Example 1:

Input: 2
Output:  2
Explanation:  There are two ways to climb to the top.

1. 1 step + 1 step
2. 2 steps

Example 2:

Input: 3
Output:  3
Explanation:  There are three ways to climb to the top.

1. 1 step + 1 step + 1 step
2. 1 step + 2 steps
3. 2 steps + 1 step

給定樓層數目,輸出有多少種攀爬方式每次能爬1或者2層

  //斐波那契數列f(n) = f(n-1) + f(n -2)
    public static int climbStairs(int n) {
        if(n ==1){
          return 1;
        }
        if(n ==2){
          return 2;
        }
        int f1 = 1;
        int f2 = 2;
        for (int i = 3; i <=n; i++) {
            int f3 = f1 + f2;
            f1 = f2;
            f2 = f3;
        }
        return f2;
       // return climbStairs(n-1) + climbStairs(n-2);
    }