Hard

Quiz

#76 Minimum Window Substring

APPROACH

Find the shortest substring of s that contains every character in t including duplicates. Return "" if no such window exists. The answer is guaranteed to be 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.

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What is the optimal approach for this problem?