【LeetCode】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?
思路：斐波拉契数
f（n）=f（n-1）+f（n-2）（n>2）,f(0)=1;f(1)=1;f(2)=2.

class Solution {
public:
int climbStairs(int n) {
int result[]={0,1,2};
if(n<=2){
return result
;
}
int prenum=result[2],frontnum=result[1],tmp;
for(int i=3;i<=n;i++){
tmp=prenum;
prenum+=frontnum;
frontnum=tmp;
}
return prenum;
}
};