find pair in unsorted array which gives sum x

1// C++ program to check if given array 
2// has 2 elements whose sum is equal 
3// to the given value 
4  
5#include <bits/stdc++.h> 
6using namespace std; 
7  
8// Function to check if array has 2 elements 
9// whose sum is equal to the given value 
10bool hasArrayTwoCandidates(int A[], int arr_size, 
11                           int sum) 
12{ 
13    int l, r; 
14  
15    /* Sort the elements */
16    sort(A, A + arr_size); 
17  
18    /* Now look for the two candidates in  
19       the sorted array*/
20    l = 0; 
21    r = arr_size - 1; 
22    while (l < r) { 
23        if (A[l] + A[r] == sum) 
24            return 1; 
25        else if (A[l] + A[r] < sum) 
26            l++; 
27        else // A[i] + A[j] > sum 
28            r--; 
29    } 
30    return 0; 
31} 
32  
33/* Driver program to test above function */
34int main() 
35{ 
36    int A[] = { 1, 4, 45, 6, 10, -8 }; 
37    int n = 16; 
38    int arr_size = sizeof(A) / sizeof(A[0]); 
39  
40    // Function calling 
41    if (hasArrayTwoCandidates(A, arr_size, n)) 
42        cout << "Array has two elements with given sum"; 
43    else
44        cout << "Array doesn't have two elements with given sum"; 
45  
46    return 0; 
47}