09. Abnormal jump step

topic

A frog can jump 1 step at a time, or 2 steps ... it can also jump to n levels. Ask the frog how many ways to jump on an n-level step.

Code

public class Solution {
	//每个台阶都有跳与不跳两种情况（除了最后一个台阶），最后一个台阶必须跳。所以共2^(n-1)中情况 
    public int JumpFloorII(int target) {
        if(target < 2){
            return target;
        }else{
            int result = 2;
            for(int i = 2; i < target; i++){
                result = result*2;
            }
            return result;
        }
    }
}