跳台阶

public class Solution {
    
    // 递归 类似斐波那契数列
    /*
    public int JumpFloor(int target) {
        if(target<=1){
            return 1;
        }
        if(target == 2){
            return 2;
        }
        return JumpFloor(target-2)+JumpFloor(target-1);
    }
    */
    
    // 动态规划
    public int JumpFloor(int target){
        if(target<=1){
            return 1;
        }
        
        int last=1;
        int lastLast=1;
        int now=0;
        
        for(int i=2; i<=target; i++){
            now = last + lastLast;
            lastLast = last;
            last = now;
        }
        return now;
    }
}