LeetCode-in-All

76. Minimum Window Substring

Hard

Given two strings s and t of lengths m and n respectively, return the minimum window substring of s such that every character in t (including duplicates) is included in the window. If there is no such substring__, return the empty string "".

The testcases will be generated such that the answer is unique.

A substring is a contiguous sequence of characters within the string.

Example 1:

Input: s = “ADOBECODEBANC”, t = “ABC”

Output: “BANC”

Explanation: The minimum window substring “BANC” includes ‘A’, ‘B’, and ‘C’ from string t.

Example 2:

Input: s = “a”, t = “a”

Output: “a”

Explanation: The entire string s is the minimum window.

Example 3:

Input: s = “a”, t = “aa”

Output: “”

Explanation: Both ‘a’s from t must be included in the window. Since the largest window of s only has one ‘a’, return empty string.

Constraints:

• m == s.length
• n == t.length
• 1 <= m, n <= 105
• s and t consist of uppercase and lowercase English letters.

Follow up: Could you find an algorithm that runs in O(m + n) time?

Solution

/**
 * @param {string} s
 * @param {string} t
 * @return {string}
 */
var minWindow = function(s, t) {
    const map = new Array(128).fill(0)

    for (let i = 0; i < t.length; i++) {
        map[t.charCodeAt(i)]++
    }

    let count = t.length
    let begin = 0
    let end = 0
    let d = Number.MAX_VALUE
    let head = 0

    while (end < s.length) {
        if (map[s.charCodeAt(end++)]-- > 0) {
            count--
        }

        while (count === 0) {
            if (end - begin < d) {
                d = end - begin
                head = begin
            }
            if (map[s.charCodeAt(begin++)]++ === 0) {
                count++
            }
        }
    }

    return d === Number.MAX_VALUE ? '' : s.substring(head, head + d)
};

export { minWindow }

This site is open source. Improve this page.