Introduction to Algorithm Design（目前學習中）

常見搜尋演算法

1. 線性搜尋 (Linear Search)

最基本的搜尋方式，從頭到尾逐一檢查。

function linearSearch(arr, target) {
  for (let i = 0; i < arr.length; i++) {
    if (arr[i] === target) {
      return i;  // 找到目標，返回索引
    }
  }
  return -1;  // 未找到目標
}

💡

Worst Case Performance: O(n)
Best Case Performance: O(1)
Average Performance: O(n/2)

2. 二分搜尋 (Binary Search)

適用於已排序的數列，每次將搜尋範圍減半。

function binarySearch(arr, target) {
  let left = 0;
  let right = arr.length - 1;
  
  while (left <= right) {
    const mid = Math.floor((left + right) / 2);
    if (arr[mid] === target) {
      return mid;
    } else if (arr[mid] < target) {
      left = mid + 1;
    } else {
      right = mid - 1;
    }
  }
  return -1;
}

💡

Worst Case Performance: O(log n)
Best Case Performance: O(1)
Average Performance: O(log n)

3. 計數器模式 (Counter)

使用計數器追蹤特定元素的出現次數。

function countCombinedElements(arr1, arr2) {
  let result = [];
  const combinedArray = arr1.concat(arr2);
  const counter = {};

  for (const element of combinedArray) {
    counter[element] = (counter[element] || 0) + 1;
  }
  
  for (let property in counter) {
    if (counter[property] >= 2) {
      result.push(property);
    }
  }

  return result;
}

💡

Worst Case Performance: O(n)
Best Case Performance: O(n)
Average Performance: O(n)