查找算法复习（1）--二分查找法

来源：互联网发布：胎动检测的软件编辑：程序博客网时间：2024/05/17 00:15

二分查找法要求被查找的线性表已经排序。

每一次查找，按中间索引把表分为左右两部分，通过对比中间值与目标值的大小，决定下一次查找在左表还是右表，直到无法再分割。

 1         public static int BinarySearch(string[] datalist, string key) 2         { 3             int low = 0; 4             int high = datalist.Length - 1;//两个下标，决定查找的区间 5             int middle; 6             while (low <= high)//无法再分割就结束 7             { 8                 middle = (low + high) / 2;//中间下标 9                 if (datalist[middle].CompareTo(key) > 0)//与中间值比较，缩小查找区间10                     high = middle - 1;11                 else if (datalist[middle].CompareTo(key) < 0)12                     low = middle + 1;13                 else14                     return middle;15             }16             return -1;17         }

使用

 1             string[] a = new string[] { "khlin", "hzluo", "jjguo", "hhchen", "jxhan", "lxiao", "jsxiao", "wwang", "lsxie", "lwang" }; 2             3             SelectedSort(a); 4             foreach(string stra in a) 5                 Console.Write("{0}, ",stra); 6             Console.WriteLine(); 7             string target1 = "jjguo"; 8             Console.WriteLine("{0} index: {1}", target1, BinarySearch(a, target1)); 9             string target2 = "lsxie";10             Console.WriteLine("{0} index: {1}", target2, BinarySearch(a, target2));11             string target3 = "hello";12             Console.WriteLine("{0} index: {1}", target3, BinarySearch(a, target3));

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