[LeetCode] [Climbing Stairs 2012-04-03]

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?

class Solution {
public:
int climbStairs(int n) {
int sum_pre = 2;
int sum_prepre =1;
if(n == 1) return sum_prepre;
if(n == 2) return sum_pre;
int sum = 0;
for(int i = 2; i < n; i++)
{
sum = sum_prepre + sum_pre;
sum_prepre = sum_pre;
sum_pre = sum;
}
return sum;
}
};