变态跳台阶_JAVA_简单

• 设跳上n阶台阶的次数为f(n)，跳上n阶台阶可以转换为最后一步上台阶，两步上台阶...n步上台阶，即为f(n) = S(n - 1)
• 转换：

  由 f(n) = S(n - 1)
  则 f(n) = S(n - 1) = f(n - 1) + S(n - 2) = 2f(n - 1)

public class Solution {
    public int JumpFloorII(int target) {
        if(target <= 1) return 1;
        // f(n) = 2f(n - 1)
        return (int)Math.pow(2,target - 1);
    }
}