Algorithm | Binary Search

 1 class BinarySearch {
 2 public:
 3     BinarySearch() {}
 4     int find(Sort& arr, int value) {
 5         int l = 0, h = arr.size() - 1; 
 6         while (l <= h) {
 7             int mid = (l + h) / 2;
 8             if (value == arr[mid]) return mid;
 9             else if (value > arr[mid]) {
10                 l = mid + 1;    
11             } else {
12                 h = mid - 1;
13             }
14         }
15         return -1;
16     }
17 
18     int findLeftMost(Sort& arr, int value) {
19         int l = 0, h = arr.size() - 1; 
20         while (l <= h) {
21             int mid = (l + h) / 2;
22             if (arr[mid] >= value) {
23                 h = mid - 1;
24             } else {
25                 l = mid + 1;    
26             }
27         }
28         if (l >= arr.size() || arr[l] != value) return -1;
29         else return l;
30     }
31     
32     int findRightMost(Sort& arr, int value) {
33         int l = 0, h = arr.size() - 1; 
34         while (l <= h) {
35             int mid = (l + h) / 2;
36             if (arr[mid] > value) {
37                 h = mid - 1;
38             } else {
39                 l = mid + 1;    
40             }
41         }
42         if (h < 0 || arr[h] != value) return -1;
43         else return h;
44     }
45 };