Efficient appraoch
- In this approach, We must efficiently determine the count of distinct pairs of characters in linear time.
- Notably, pairs like (x, y) and (y, x) are treated as distinct.
- To accomplish this, we employ a hash table to record the occurrences of each character. If a character appears twice, it corresponds to 4 pairs: (i, i), (j, j), (i, j), and (j, i).
- By utilizing a hashing mechanism, we keep track of the frequency of each character, and for each character, the count of pairs will be the square of its frequency.
- The hash table will have a length of 256 since there are 256 distinct characters.
Example: This example shows the use of the above-explined approach.
// JavaScript program to calculate the
// count of pairs
const MAX = 256
// Function to calculate the count
// of identical pairs
function fun(str) {
// Hash table to store
// character counts
let charCount = new Array(MAX).fill(0)
// Iterate through the string and tally
// the occurrences of each character
for (let i = 0; i < str.length; i++)
charCount[str.charCodeAt(i) - 97] += 1
// Variable to hold the final count of pairs
let pairCount = 0
// Iterate through the characters and check
// for occurrences
for (let i = 0; i < MAX; i++)
pairCount += charCount[i] * charCount[i]
return pairCount
}
// Driver code
let str = "pqr"
console.log(fun(str))
Output
3
Time Complexity: O(n), n is the length of input string
Space Complexity: O(1)
JavaScript Program Count number of Equal Pairs in a String
In this article, we are going to learn how can we count a number of equal pairs in a string. Counting equal pairs in a string involves finding and counting pairs of consecutive characters that are the same. This task can be useful in various applications, including pattern recognition and data analysis.
Examples:
Input: 'pqr'
Output: 3
Explanation:
3 pairs that are equal are (p, p), (q, q) and (r, r)
Input: 'HelloWorld'
Output: 18
Table of Content
- Naive Approach
- Efficient appraoch
- Using a Map to Count Characters
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