/**

* @param {string} s

* @param {string} t

* @return {string}

*/

var minWindow = function(s, t) {

if (s.length === 0 || t.length === 0) return "";

const dictT = {};

for (let char of t) {

dictT[char] = (dictT[char] || 0) + 1;

}

const required = Object.keys(dictT).length;

let formed = 0;

const windowCounts = {};

let left = 0, right = 0;

let minLen = Infinity;

let minLeft = 0, minRight = 0;

while (right < s.length) {

const character = s[right];

windowCounts[character] = (windowCounts[character] || 0) + 1;

if (dictT[character] && windowCounts[character] === dictT[character]) {

formed++;

}

while (left <= right && formed === required) {

const currentLen = right - left + 1;

if (currentLen < minLen) {

minLen = currentLen;

minLeft = left;

minRight = right;

}

const leftChar = s[left];

windowCounts[leftChar]--;

if (dictT[leftChar] && windowCounts[leftChar] < dictT[leftChar]) {

formed--;

}

left++;

}

right++;

}

return minLen === Infinity ? "" : s.substring(minLeft, minRight + 1);

};