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.
class Solution {
public:
int climbStairs(int n) {
if(n==1) return 1;
if(n==2) return 2;
int i=3,res=3,imax=n+1,t1=1,t2=2;
while(i<imax){
res=t1+t2;
t1=t2;
t2=res;
++i;
}
return res;
}
};