剑指offer题七

package jianzhioffer;import java.util.Scanner;/** * 一只青蛙一次可以跳上1级台阶，也可以跳上2级。求该青蛙跳上一个n级的台阶总共有多少种跳法。  *  */public class Solution7 {//自顶向下，使用递归/*public static int JumpFloor(int target) {         if(target == 1){         return 1;         }else if(target ==2 ){         return 2;         }else{         return JumpFloor(target-1) + JumpFloor(target-2);         }    }*///自底向上，使用迭代public static int JumpFloor(int target) {if(target == 0){return 1;}if(target == 1)return 1;int s1 = 1;int s2 = 1;int result = 0;for(int i = 2;i<=target;i++){result = s1+s2;s2 = s1;s1 = result;}return result;}public static void main(String[] args) {Scanner sc = new Scanner(System.in);int target = sc.nextInt();int sum = JumpFloor(target);        System.out.println(sum);}}