567.permutation-in-string.js

/*
 * @lc app=leetcode id=567 lang=javascript
 *
 * [567] Permutation in String
 */

// @lc code=start
/**
 * @param {string} s1
 * @param {string} s2
 * @return {boolean}
 */
 var checkInclusion = function (s1, s2) {
	if (s1.length > s2.length) return false;
	let neededChar = {};
	for (let i = 0; i < s1.length; i++) {
		neededChar[s1[i]] = (neededChar[s1[i]] || 0) + 1;
	}
	let left = 0,
		right = 0,
		requiredLength = s1.length;
	while (right < s2.length) {
		if (neededChar[s2[right]] > 0) requiredLength--;
		neededChar[s2[right]]--;
		right++
		if (requiredLength === 0) return true;
		if (right - left === s1.length) {
			if (neededChar[s2[left]] >= 0) requiredLength++;
			neededChar[s2[left]]++;
			left++
		}
	}
	return false;
};
// @lc code=end