每天一道剑指offer-牛客网跳台阶

public class Solution {
    public int JumpFloor(int target) {
        if(target == 1)
            return 1;
        if(target == 2)
            return 2;
        int a = 1;
        int b = 2;
        int sum = a + b;
        for(int i=3;i<=target;i++)
        {
            sum = a + b;
            a = b;
            b = sum;
        }
        return sum;
    }
}