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?

• 这道题其实考的就是青蛙跳台阶的问题，本质是斐波那契数列。f(n+2) = f(n) + f(n+1).

• C++ AC代码如下：

class Solution {
public:
int climbStairs(int n) {
    if(n == 1 || n == 2)
        return n;

    int f0 = 1, f1 = 1;
    int steps = 0;

    for(int i=2; i<=n; i++)
    {
        steps = f0 + f1;
        f0 = f1;
        f1 = steps;
    }

    return steps;
}
};