RemoveAllAdjacentDuplicatesInString.js

// Source : https://leetcode.com/problems/remove-all-adjacent-duplicates-in-string/
// Author : Dean Shi
// Date   : 2019-05-24

/***************************************************************************************
 *
 * Given a string S of lowercase letters, a duplicate removal consists of choosing two
 * adjacent and equal letters, and removing them.
 *
 * We repeatedly make duplicate removals on S until we no longer can.
 *
 * Return the final string after all such duplicate removals have been made.  It is
 * guaranteed the answer is unique.
 *
 * Example 1:
 *
 * Input: "abbaca"
 * Output: "ca"
 * Explanation:
 * For example, in "abbaca" we could remove "bb" since the letters are adjacent and
 * equal, and this is the only possible move.  The result of this move is that the
 * string is "aaca", of which only "aa" is possible, so the final string is "ca".
 *
 * Note:
 *
 * 1 <= S.length <= 20000
 * S consists only of English lowercase letters.
 *
 ***************************************************************************************/

/**
 * @param {string} S
 * @return {string}
 */
var removeDuplicates = function(S) {
    const stack = [S[0]]
    for (let i = 1; i < S.length; i++) {
        const char = stack.pop()
        if (char !== S[i]) {
            stack.push(char, S[i])
        }
    }
    return stack.join('')
};