412.Fizz-Buzz

412. Fizz Buzz

题目地址

https://leetcode.com/problems/fizz-buzz/

题目描述

Write a program that outputs the string representation of numbers from 1 to n.

But for multiples of three it should output “Fizz” instead of the number and for the multiples of five output “Buzz”. For numbers which are multiples of both three and five output “FizzBuzz”.

Example:
n = 15,

Return:
[
    "1",
    "2",
    "Fizz",
    "4",
    "Buzz",
    "Fizz",
    "7",
    "8",
    "Fizz",
    "Buzz",
    "11",
    "Fizz",
    "13",
    "14",
    "FizzBuzz"
]

代码

Approach #1 Naive Approach

class Solution {
  public List<String> fizzBuzz(int n) {
        List<String> ans = new ArrayList<String>();
    for (int num = 1; num <= n; num++) {
      boolean divisibleBy3 = (num % 3 == 0);
      boolean divisibleBy5 = (num % 5 == 0);

      if (divisibleBy3 && divisibleBy5) {
        ans.add("FizzBuzz");
      } else if (divisibleBy3) {
        ans.add("Fizz");
      } else if (divisibleBy5) {
        ans.add("Buzz");
      } else {
        ans.add(Integer.toString(num));
      }
    }

    return ans;
  }
}

Approach #2 String Concatenation

class Solution {
  public List<String> fizzBuzz(int n) {
    // ans list
    List<String> ans = new ArrayList<String>();

    for (int num = 1; num <= n; num++) {

      boolean divisibleBy3 = (num % 3 == 0);
      boolean divisibleBy5 = (num % 5 == 0);

      String numAnsStr = "";

      if (divisibleBy3) {
        // Divides by 3, add Fizz
        numAnsStr += "Fizz";
      }

      if (divisibleBy5) {
        // Divides by 5, add Buzz
        numAnsStr += "Buzz";
      }

      if (numAnsStr.equals("")) {
        // Not divisible by 3 or 5, add the number
        numAnsStr += Integer.toString(num);
      }

      // Append the current answer str to the ans list
      ans.add(numAnsStr);
    }

    return ans;
  }
}

Approach #3 Hash it

class Solution {
  public List<String> fizzBuzz(int n) {

    // ans list
    List<String> ans = new ArrayList<String>();

    // Hash map to store all fizzbuzz mappings.
    HashMap<Integer, String> fizzBizzDict =
        new HashMap<Integer, String>() {
          {
            put(3, "Fizz");
            put(5, "Buzz");
          }
        };

    for (int num = 1; num <= n; num++) {

      String numAnsStr = "";

      for (Integer key : fizzBizzDict.keySet()) {

        // If the num is divisible by key,
        // then add the corresponding string mapping to current numAnsStr
        if (num % key == 0) {
          numAnsStr += fizzBizzDict.get(key);
        }
      }

      if (numAnsStr.equals("")) {
        // Not divisible by 3 or 5, add the number
        numAnsStr += Integer.toString(num);
      }

      // Append the current answer str to the ans list
      ans.add(numAnsStr);
    }

    return ans;
  }
}