为什么一个线性搜索给我的输出与另一个不同？

Question

我正在转换算法解锁书中提供的伪代码。

第一个伪代码如下：

Procedure LINEAR-SEARCH (A; n; x)
Inputs:
   A: an array.
   n: the number of elements in A to search through.
   x: the value being searched for.
Output: Either an index i for which A[i] = x, or the special value NOT-FOUND, which could be any invalid index into the array, such as 0 or any negative integer.
1. Set answer to NOT-FOUND.
2. For each index i, going from 1 to n, in order:
   A. If A[i] = x, then set answer to the value of i. 
3. Return the value of answer as the output.

这是用 Javascript 解决此伪代码的一个版本：

版本 1：输出：将 i 返回为 5

function linearSearch(data, searchQuery) {
  var answer = 'not found';
  for (var i = 0, len = data.length; i < len; i++) {
    if (data[i] === searchQuery) {
      answer = i;
    }
  }
  return answer;
}

var names = ["Jack", "Molly", "Tristan", "Jacob", "Jacob", "Jacob", "Steph"]
var result = linearSearch(names, "Jacob");
console.log(result);

这是另一个：

版本 2：输出：将 i 返回为 3

var answer = 'not found';

function LinearSearch(A,n,searchQuery) {
  var answer = 'not found';
  for (var i = 0; i < A.length; i++) {
    if (A[i] === searchQuery) {
      return i;
    }
  }
  return answer;
}

var names = ["Jack", "Molly", "Tristan", "Jacob", "Jacob", "Jacob", "Steph"];
var result = LinearSearch(names, names.length, "Jacob");

我在代码中做了什么来实现两个不同的输出？

Answer 1

您的第一个函数不会在找到匹配项后立即退出循环，但第二个函数会。

在第一个中，当i 为3、4 和5 时，本地answer 变量将设置为i。最后一个值是5，所以这就是返回的值。

for (var i = 0, len = data.length; i < len; i++) {
  if (data[i] === searchQuery) {
    answer = i; // update answer - LOOP CONTINUES
  }
}

在第二个中，一旦找到匹配项，函数就会返回该索引：

  for (var i = 0; i < A.length; i++) {
    if (A[i] === searchQuery) {
      return i; // return index immediately and stop iterating
    }
  }