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  1. // Count Occurrence (Lower & Upper Bound)
  2. #include <bits/stdc++.h>
  3. using namespace std;
  4.  
  5. int lowerBound(vector<int>& arr, int x) {
  6.     int l = 0, r = arr.size();
  7.     while(l < r) {
  8.         int mid = l + (r - l) / 2;
  9.         if(arr[mid] < x) l = mid + 1;
  10.         else r = mid;
  11.     }
  12.     return l;
  13. }
  14.  
  15. int upperBound(vector<int>& arr, int x) {
  16.     int l = 0, r = arr.size();
  17.     while(l < r) {
  18.         int mid = l + (r - l) / 2;
  19.         if(arr[mid] <= x) l = mid + 1;
  20.         else r = mid;
  21.     }
  22.     return l;
  23. }
  24.  
  25. int main() {
  26.     int n = 6, x = 2;
  27.     vector<int> arr = {1,2,2,2,3,4};
  28.     cout << upperBound(arr, x) - lowerBound(arr, x);
  29. }
Success #stdin #stdout 0s 5320KB
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https://ideone.com/bZKHP2
language:
C++ (gcc 8.3)
created:
18 hours ago
visibility:
public

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