【LeetCode】70 - Climbing Stairs

 1 int climbStairs(int n) {    //Runtime:0ms
 2     int a=1,b=2;
 3     if(n==1)return a;
 4     if(n==2)return b;
 5     int c=0;
 6     for(int i=3;i<=n;i++){
 7         c=a+b;
 8         a=b;
 9         b=c;
10     }
11     return c;
12 }
13 int climbStairs2(int n){    ////Runtime:0ms
14     if(n <= 2)return n;
15     int* step = new int[n];  
16     step[0] = 1;  
17     step[1] = 2;  
18     for(int i = 2; i < n; i++)step[i] = step[i-1] + step[i-2];  
19     return step[n-1];  
20 }