查找算法简介及实现

  1 //查找算法：
  2 //        顺序查找
  3 //        二分查找（插值查找，斐波那契查找）
  4 //        二叉排序树查找
  5 //        哈希表查找
  6 
  7 #include <iostream>
  8 using namespace std;
  9 
 10 
 11 /*顺序查找*/
 12 int sequenceSearch(int* arr, int len, int n)
 13 {
 14     for (int i = 0; i < len; i++)
 15         if (arr[i] == n)
 16             return i;
 17 
 18     return -1;
 19 }
 20 
 21 /*二分查找（非递归版本）*/
 22 int binarySearch(int* arr, int len, int n)
 23 {
 24     int low = 0, high = n - 1, mid;
 25     while (low <= high)
 26     {
 27         mid = (low + high) >> 1;
 28         if (arr[mid] == n)
 29             return mid;
 30         else if (arr[mid] < n)
 31             low = mid + 1;
 32         else
 33             high = mid - 1;
 34     }
 35 
 36     return -1;
 37 }
 38 
 39 /*二分查找（递归版本）*/
 40 int binarySearch0(int* arr, int n, int low, int high)
 41 {
 42     if (low <= high)
 43     {
 44         int mid = (low + high) >> 1;
 45 
 46         if (arr[mid] == n)
 47             return mid;
 48         else if (arr[mid] < n)
 49             binarySearch0(arr, n, mid + 1, high);
 50         else
 51             binarySearch0(arr, n, low, mid - 1);
 52     }
 53 
 54     return -1;
 55 }
 56 
 57 /*插值查找*/
 58 int insertSearch(int* arr, int len, int n)
 59 {
 60     int low = 0, high = len - 1, mid;
 61     while (low <= high)
 62     {
 63         if (arr[low] == arr[high]) //处理数组中具有相同值的情况
 64             if (arr[low] == n)
 65                 return low;
 66             else
 67                 return -1;
 68 
 69         mid = (int)(1.0*(n - arr[low]) / (arr[high] - arr[low])*(high - low)); //需要转换为double进行计算
 70         if (arr[mid] == n)
 71             return mid;
 72         else if (arr[mid] < n)
 73             low = mid + 1;
 74         else
 75             high = mid - 1;
 76     }
 77 
 78     return -1;
 79 }
 80 
 81 
 82 
 83 int main()
 84 {
 85     cout << "请输入数组序列和带查找元素\n（格式：序列长度n 元素1 元素2 ... 元素n 带查找元素num）: " << endl;
 86     int n, *parr, num;
 87     cin >> n;
 88     parr = new int[n];
 89     for (int i = 0; i < n; i++)
 90         cin >> parr[i];
 91     cin >> num;
 92 
 93     cout << "\n1 顺序查找； 2 二分查找（非递归）； 3 二分查找（递归）； 4 插值查找；\n";
 94     cout << "请选择查找模式：";
 95     int selection, index;
 96     while (cin >> selection)
 97     {
 98         switch (selection)
 99         {
100         case 1:
101             index = sequenceSearch(parr, n, num);
102             break;
103         case 2:
104             index = binarySearch(parr, n, num);
105             break;
106         case 3:
107             index = binarySearch0(parr, num, 0, n - 1);
108             break;
109         case 4:
110             index = insertSearch(parr, n, num);
111             break;
112         default:
113             break;
114         }
115 
116         if (index == -1)
117             cout << "查找失败！" << endl;
118         else
119             cout << "查找成功！位置：" << index + 1 << endl;
120 
121         cout << "\n请选择查找模式：";
122     }
123 
124     return 0;
125 }