Question

How to count the number of substrings with exactly k distinct characters in JavaScript

Answer 1

function CountSubstringWithKDistinctChars(s, k) {
    let count = 0;
    
    for (let i = 0; i < s.length; i++) {
        let ch = s.charAt(i);
        let tmp = "" + ch;
        let set = new Set();
        set.add(ch);
        
        for (let j = i + 1; j < s.length; j++) {
            const next_ch = s.charAt(j);
            set.add(next_ch);
            tmp += next_ch;
            if (tmp.length >= k && set.size == k) {
                    count++;
            }
        }
    }
    return count;
}

const str = "characters";
const k = 4;

console.log("Number of substrings with exactly k distinct characters = " + CountSubstringWithKDistinctChars(str, k));




/*
run:

Number of substrings with exactly k distinct characters = 9

*/

 

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