Minimum Window Substring

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Problem

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.

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.

Pseudocode

Solution

// from solutions
// https://leetcode.com/problems/minimum-window-substring/solutions/26808/here-is-a-10-line-template-that-can-solve-most-substring-problems/
var minWindow = function (s, t) {
  let counter = t.length;
  let shortestSubstring = "";
  const tMap = {};
  let start = 0;
  let end = 0;
  let minStart = 0;
  let minLen = Infinity;
  let size = s.length;

  for (let i = 0; i < t.length; i++) {
    if (!tMap[t[i]]) {
      tMap[t[i]] = 0;
    }
    tMap[t[i]] += 1;
  }

  while (end < size) {
    if (tMap[s[end]] > 0) {
      counter--;
    }

    tMap[s[end]]--;
    end++;
    console.log(tMap);
    while (counter === 0) {
      if (end - start < minLen) {
        minStart = start;
        minLen = end - start;
      }

      tMap[s[start]]++;
      console.log(tMap);
      if (tMap[s[start]] > 0) {
        counter++;
      }
      start++;
    }
  }
  console.log(tMap);
  if (minLen !== Infinity) {
    shortestSubstring = s.substring(minStart, minStart + minLen);
  }

  return shortestSubstring;
};

Time and Space Complexity

Time

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Space

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