Getting a Pair whose Sum = K

Obtaining a pair of elements in the array whose sum = k.

For Sorted Arrays:

void findPair(int a[], int n, int key) {
​
// Set i to starting index and j to last index
int i = 0, j = n-1;
while (i < j) {
// If pair is found, increment i and decrement j
if (a[i] + a[j] == key) {
printf("Pair : %d and %d\n", a[i], a[j]);
i++;
j--;
}
// If sum is greater than key, decrement j
else if (a[i] + a[j] > key) {
j--;
}
// If sum is smaller than key, increment i
else {
i++;
}
}
​
}

For Unsorted Arrays:

void findPair(int a[], int n, int max, int key) {
// Create and initialize hash array with 0
int h[max];
for (int i = 0; i < max; i++) {
h[i] = 0;
}
for (int i = 0; i < n; i++) {
// Check if the suitable pair is present
if (h[key - a[i]] != 0) {
printf("Pair : %d and %d\n", a[i], key-a[i]);
}
h[a[i]]++;
}
​
}
Contributed by Nitin Ranganath