lintcode-easy-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?

Example

Given an example n=3 , 1+1+1=2+1=1+2=3

return 3

 

动态规划里思路比较容易理清的一题，要走到第n个台阶有两种选择，要么从第n-1阶走一个台阶上来，要么从第n-2阶走两个台阶上来。

public class Solution {
    /**
     * @param n: An integer
     * @return: An integer
     */
    public int climbStairs(int n) {
        // write your code here
        if(n == 0)
            return 1;
        if(n == 1)
            return 1;
        if(n == 2)
            return 2;
        
        int[] result = new int[n + 1];
        result[0] = 1;
        result[1] = 1;
        result[2] = 2;
        
        for(int i = 3; i <= n; i++)
            result[i] = result[i - 1] + result[i - 2];
        
        return result[n];
    }
}