20151215笔记：查找算法——顺序查找和二分查找

来源：互联网发布：赌博庄家抽水算法编辑：程序博客网时间：2024/05/29 18:05

顺序查找：线性查找，从前往后依次查找，直到找到匹配的值，返回键值或其下标；若无匹配值返回 -1。代码如下：

<pre name="code" class="java"><span style="font-family:Arial;font-size:18px;">public class LinearSearch{<span style="white-space: pre;"></span>public static int linearSearch(int[] list, int key){</span>

<span style="font-family:Arial;font-size:18px;"><span style="white-space:pre"></span>for(int i=0;i<list.length;i++){</span>

<span style="font-family:Arial;font-size:18px;"><span style="white-space:pre"></span>if(key==list[i]) return i;</span>

<span style="font-family:Arial;font-size:18px;"><span style="white-space:pre"></span>}</span>

<span style="font-family:Arial;font-size:18px;"><span style="white-space:pre"></span>return -1;</span>

<span style="font-family:Arial;font-size:18px;"><span style="white-space: pre;"></span>}}</span>

<span style="font-family:Arial;font-size:18px;"></span>

<span style="font-family:Arial;font-size:18px;">二分查找：适合有序数组。键值和数组中间元素比较，若小于中间元素，查找前半部分的中间元素与之比较，反之查找后半部分；依次类推，直到找到为止。</span>

<span style="font-family:Arial;font-size:18px;">public class BinarySearch{</span>

<span style="white-space:pre"></span><span style="font-family:Arial;font-size:18px;">public static int binarySearch(int[] list, int key){</span>

<span style="font-family:Arial;font-size:18px;"><span style="white-space:pre"></span> <span style="white-space:pre"></span>int low=0;</span>

<span style="font-family:Arial;font-size:18px;"><span style="white-space:pre"></span>int high=list.length-1;</span>

<span style="font-family:Arial;font-size:18px;"><span style="white-space:pre"></span>while(high>=low){</span>

<span style="font-family:Arial;font-size:18px;"><span style="white-space:pre"></span>int mid=(low+high)/2;</span>

<span style="font-family:Arial;font-size:18px;"><span style="white-space:pre"></span>if(key<list[mid])</span>

<span style="font-family:Arial;font-size:18px;"><span style="white-space:pre"></span>high=mid-1;</span>

<span style="font-family:Arial;font-size:18px;"><span style="white-space:pre"></span>else if(key==list[mid])</span>

<span style="font-family:Arial;font-size:18px;"><span style="white-space:pre"></span>return mid;</span>

<span style="font-family:Arial;font-size:18px;"><span style="white-space:pre"></span>else</span>

<span style="font-family:Arial;font-size:18px;"><span style="white-space:pre"></span>low=mid+1;</span>

<span style="font-family:Arial;font-size:18px;"><span style="white-space:pre"></span>}</span>

<span style="font-family:Arial;font-size:18px;"><span style="white-space:pre"></span>return -low-1;<span style="white-space:pre"></span></span>

<span style="font-family:Arial;font-size:18px;"><span style="white-space:pre"></span>}</span>

</pre><pre name="code" class="java">

<span style="font-family:Arial;font-size:18px;">}</span>

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