mostFrequent.js (7kyu 83)

in about Dev on Algorithm

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Problem

  • Complete the function to find the count of the most frequent item of an array.
    • 배열에서 가장 빈번한 item의 수를 반환한다.
  • For an empty array return 0.
    • 빈 배열의 경우 0을 반환한다.


Solution 01

function mostFrequent(arr) {
  let count = 0;
  let frequentCount = 0;
  
  for (let i = 0; i < arr.length; i++) {
    for (let j = 0; j < arr.length; j++) {
      if (arr[i] === arr[j]) {
        count++;
      }
      
      if (count > frequentCount) {
        frequentCount = count;
      }
    }
    count = 0;
  }
  return frequentCount;
}

mostFrequent([]);            // 0
mostFrequent([4, 2, 9, 4]);  // 2
mostFrequent([8, 6, 8, 8]);  // 3


Solution 02

function mostFrequent(arr) {
  let frequency = {};
  let max = 0;
  
  for (let i = 0; i < arr.length; i++) {
    frequency[arr[i]] = frequency[arr[i]] ? frequency[arr[i]] + 1 : 1;
    
    if (max < frequency[arr[i]]) {
      max = frequency[arr[i]];
    }
  }
  return max;
}

mostFrequent([]);            // 0
mostFrequent([4, 2, 9, 4]);  // 2
mostFrequent([8, 6, 8, 8]);  // 3


Solution 03

function mostFrequent(arr) {
  if (arr.length) {
    let frequency = {};
    let max = 0;
    
    for (let i = 0; i < arr.length; i++) {
      frequency[arr[i]] = (frequency[arr[i]] || 0) + 1
      
      if (max < frequency[arr[i]]) {
        max = frequency[arr[i]];
      }
    }
    return max;
  }
  return 0;
}

mostFrequent([]);            // 0
mostFrequent([4, 2, 9, 4]);  // 2
mostFrequent([8, 6, 8, 8]);  // 3