IsFibo 未返回所需结果

Question

这是我想到的解决 IsFibo HackerRank 问题的方法。 (https://www.hackerrank.com/challenges/is-fibo)。我想知道为什么它不会 return "IsFibo" 5。我的逻辑可能有问题，如果有人指出我的错误，我将不胜感激。这是代码：

import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {
    public static ArrayList<BigInteger> fibList = new ArrayList<BigInteger>();

    public static void main(String[] args) {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */
        Scanner in = new Scanner(System.in);
        int numCases = in.nextInt();

        fibList.add(BigInteger.valueOf(0));
        fibList.add(BigInteger.valueOf(1));

        while(in.hasNextLine()) {
            System.out.println(checkFibo(in.nextBigInteger()));
            System.out.println(fibList);
        }
    }

    public static String checkFibo(BigInteger i) {
        int lastIndex = fibList.size() - 1;
        int compareRes = i.compareTo(fibList.get(lastIndex));

        System.out.println("Last fib num: " + fibList.get(lastIndex));
        System.out.println("CompareRes: " + compareRes);

        switch(compareRes) {
            case 0:
                return "IsFibo";
            case 1:
                BigInteger newFib = fibList.get(lastIndex-1).add(fibList.get(lastIndex));
                fibList.add(newFib);
                checkFibo(i);
                break;
            default:
                break;
        }

        return "IsNotFibo";

    }
}

Answer 1

您的代码有两个问题：

情况 1：不从递归调用return传回值
属于默认实现的 case -1 被完全忽略（即代码无法处理已经处理过的较大输入后的较小输入）

这是一个工作代码：

import java.math.BigInteger;
import java.util.ArrayList;
import java.util.Scanner;

public class Solution {
    public static ArrayList<BigInteger> fibList = new ArrayList<BigInteger>();

    public static void main(String[] args) {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */
        Scanner in = new Scanner(System.in);

        fibList.add(BigInteger.valueOf(0));
        fibList.add(BigInteger.valueOf(1));

        while(in.hasNextLine()) {
            BigInteger nextBigDecimal = in.nextBigInteger();
            System.out.println("input:" + nextBigDecimal);
            System.out.println("isFibo: " + checkFibo(nextBigDecimal));
            System.out.println(fibList);
        }
    }

    public static boolean checkFibo(BigInteger i) {
        int lastIndex = fibList.size() - 1;
        int compareRes = i.compareTo(fibList.get(lastIndex));

        System.out.println("Last fib num: " + fibList.get(lastIndex));
        System.out.println("CompareRes: " + compareRes);

        boolean isFibo = false;

        switch(compareRes) {
            case 0:
                isFibo = true;
                break;
            case 1:
                BigInteger newFib = fibList.get(lastIndex-1).add(fibList.get(lastIndex));
                fibList.add(newFib);
                isFibo = checkFibo(i);
                break;
            case -1:
                isFibo = fibList.contains(i);
                break;
        }
        return isFibo;
    }
}

IsFibo 未返回所需结果

IsFibo not returning desired result

java

fibonacci