# Unique substrings in circular string in JavaScript

## Problem

Suppose we have a S, str. which is an infinite wraparound string of the string −

"abcdefghijklmnopqrstuvwxyz".

Therefore, S will look like this −

"...zabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcd....".

We are required to write a JavaScript function that takes in str, let’s call that string str, as the only argument.

• Our function should find out how many unique non-empty substrings of str are present in S.

• Our function should finally return the number of different non-empty substrings of str in the string S.

For example, if the input to the function is −

const str = "zab";

Then the output should be −

const output = 6;

## Output Explanation

There are six substrings "z", "a", "b", "za", "ab", "zab" of string "zab" in the string S.

## Example

The code for this will be −

Live Demo

const str = "zab";
const allSubstrings = (str = '') => {
const dp = new Array(26).fill(0);
dp[str.charCodeAt(0) - 97] = 1;
maxCount = 1;
for (let i = 1; i < str.length; i++) {
if ((str.charCodeAt(i) - str.charCodeAt(i - 1) == 1) || (str.charCodeAt(i) - str.charCodeAt(i - 1) == -25)) {
maxCount++;
} else {
maxCount = 1;
}
dp[str.charCodeAt(i) - 97] = Math.max(dp[str.charCodeAt(i) - 97], maxCount);
}
return dp.reduce((item, val) => {
return val + item;
})
};
console.log(allSubstrings(str));

## Output

And the output in the console will be −

6

Updated on: 04-Mar-2021

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