70. Climbing Stairs

70. 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: 2Output: 2Explanation: There are two ways to climb to the top.1. 1 step + 1 step2. 2 steps

Example 2:

Input: 3Output: 3Explanation: There are three ways to climb to the top.1. 1 step + 1 step + 1 step2. 1 step + 2 steps3. 2 steps + 1 step

public class Solution { public int climbStairs(int n) { int a=1; int b=2; if(n==1)return a; if(n==2)return b; for(int i=3;i<=n;i++){ int index=a; a=b; b=index+a; } return b; }}

class Solution { public int climbStairs(int n) { int[] memory = new int[n+1]; return climb(n, memory); } public int climb(int n, int[] memory) { if(n <= 2) { return n; } if(memory[n] != 0) { return memory[n]; } memory[n] = climb(n-1, memory) + climb(n-2, memory); return memory[n]; }}

class Solution { public int climbStairs(int n) { if (n <= 0) return 0; else if (n == 1) return 1; else if (n == 2) return 2; int[] arr = new int[n + 1]; arr[1] = 1; arr[2] = 2; for (int i = 3; i < n + 1; i++) { arr[i] = arr[i -1] + arr[i - 2]; } return arr[n]; }}

版权声明：本文内容由网络用户投稿，版权归原作者所有，本站不拥有其著作权，亦不承担相应法律责任。如果您发现本站中有涉嫌抄袭或描述失实的内容，请联系我们jiasou666@gmail.com 处理，核实后本网站将在24小时内删除侵权内容。