70. 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?

典型的动态规划问题

public class Solution {
public int climbStairs(int n) {
if (n < 1) return 0;
if (n == 1) return 1;
int oneStep = 1, twoStep = 0;
for (int i = 1; i <= n; i++) {
int t = oneStep+twoStep;
twoStep = oneStep;
oneStep = t;
}
return oneStep;
}
}