#3084 - Count Substrings Starting and Ending with Given Character

Medium • View on LeetCode • View on GitHub

Problem Description

You are given a string s and a character c. Return the total number of substrings of s that start and end with c.

Solution

/**
 * @param {string} s
 * @param {character} c
 * @return {number}
 */
var countSubstrings = function(s, c) {
  let count = 0;
  for (const char of s) {
    if (char === c) count++;
  }
  return (count * (count + 1)) / 2;
};