Count pairs of characters in a string whose ASCII value difference is K
Last Updated :
08 Feb, 2024
Given string str of lower case alphabets and a non-negative integer K. The task is to find the number of pairs of characters in the given string whose ASCII value difference is exactly K.
Examples:
Input: str = “abcdab”, K = 0
Output: 2
(a, a) and (b, b) are the only valid pairs.
Input: str = “geeksforgeeks”, K = 1
Output: 8
(e, f), (e, f), (f, e), (f, e), (g, f),
(f, g), (s, r) and (r, s) are the valid pairs.
Approach: Store the frequency of each character in an array. Traverse through this frequency array to get the required answer. There exist two cases:
- If K = 0 then check if the similar character appears more than once i.e. if freq[i] > 1. If yes then add (freq[i] * (freq[i] – 1)) / 2 to the count.
- If K != 0 then check if there exist two characters with ASCII value difference as K say freq[i] and freq[j]. Then add freq[i] * freq[j] to the count.
Below is the implementation of the above approach:
C++
#include <bits/stdc++.h>
using namespace std;
#define MAX 26
int countPairs(string str, int k)
{
int n = str.size();
int freq[MAX];
memset (freq, 0, sizeof freq);
for ( int i = 0; i < n; i++)
freq[str[i] - 'a' ]++;
int cnt = 0;
if (k == 0) {
for ( int i = 0; i < MAX; i++)
if (freq[i] > 1)
cnt += ((freq[i] * (freq[i] - 1)) / 2);
}
else {
for ( int i = 0; i < MAX; i++)
if (freq[i] > 0 && i + k < MAX && freq[i + k] > 0)
cnt += (freq[i] * freq[i + k]);
;
}
return cnt;
}
int main()
{
string str = "abcdab" ;
int k = 0;
cout << countPairs(str, k);
return 0;
}
|
Java
import java.util.Arrays;
class GFG
{
static int MAX = 26 ;
static int countPairs( char [] str, int k)
{
int n = str.length;
int [] freq = new int [MAX];
for ( int i = 0 ; i < n; i++)
{
freq[str[i] - 'a' ]++;
}
int cnt = 0 ;
if (k == 0 )
{
for ( int i = 0 ; i < MAX; i++)
{
if (freq[i] > 1 )
{
cnt += ((freq[i] * (freq[i] - 1 )) / 2 );
}
}
}
else
{
for ( int i = 0 ; i < MAX; i++)
{
if (freq[i] > 0 && i + k < MAX && freq[i + k] > 0 )
{
cnt += (freq[i] * freq[i + k]);
}
}
;
}
return cnt;
}
public static void main(String[] args)
{
String str = "abcdab" ;
int k = 0 ;
System.out.println(countPairs(str.toCharArray(), k));
}
}
|
Python3
MAX = 26
def countPairs(string, k) :
n = len (string);
freq = [ 0 ] * MAX ;
for i in range (n) :
freq[ ord (string[i]) -
ord ( 'a' )] + = 1 ;
cnt = 0 ;
if (k = = 0 ) :
for i in range ( MAX ) :
if (freq[i] > 1 ) :
cnt + = ((freq[i] *
(freq[i] - 1 )) / / 2 );
else :
for i in range ( MAX ) :
if (freq[i] > 0 and
i + k < MAX and
freq[i + k] > 0 ) :
cnt + = (freq[i] * freq[i + k]);
return cnt;
if __name__ = = "__main__" :
string = "abcdab" ;
k = 0 ;
print (countPairs(string, k));
|
C#
using System;
class GFG
{
static int MAX = 26;
static int countPairs( char [] str, int k)
{
int n = str.Length;
int [] freq = new int [MAX];
for ( int i = 0; i < n; i++)
{
freq[str[i] - 'a' ]++;
}
int cnt = 0;
if (k == 0)
{
for ( int i = 0; i < MAX; i++)
{
if (freq[i] > 1)
{
cnt += ((freq[i] * (freq[i] - 1)) / 2);
}
}
}
else
{
for ( int i = 0; i < MAX; i++)
{
if (freq[i] > 0 && i + k < MAX && freq[i + k] > 0)
{
cnt += (freq[i] * freq[i + k]);
}
}
;
}
return cnt;
}
public static void Main(String[] args)
{
String str = "abcdab" ;
int k = 0;
Console.WriteLine(countPairs(str.ToCharArray(), k));
}
}
|
Javascript
<script>
const MAX = 26;
function countPairs(str, k) {
var n = str.length;
var freq = new Array(MAX).fill(0);
for ( var i = 0; i < n; i++) {
freq[str[i].charCodeAt(0) -
"a" .charCodeAt(0)]++;
}
var cnt = 0;
if (k === 0) {
for ( var i = 0; i < MAX; i++) {
if (freq[i] > 1) {
cnt += (freq[i] * (freq[i] - 1)) / 2;
}
}
} else {
for ( var i = 0; i < MAX; i++) {
if (freq[i] > 0 && i + k < MAX &&
freq[i + k] > 0) {
cnt += freq[i] * freq[i + k];
}
}
}
return cnt;
}
var str = "abcdab" ;
var k = 0;
document.write(countPairs(str.split( "" ), k));
</script>
|
Time Complexity: O(|str| + MAX)
Auxiliary Space: O(MAX)
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