115. Minimum Window Substring

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Input: s = "ADOBECODEBANC", t = "ABC"

Output: "BANC"

Explanation: The substring "BANC" contains all characters from "ABC" and is the shortest such substring.

Input: s = "a", t = "a"

Output: "a"

Explanation: The substring "a" contains the character 'a' from "a" and is the shortest such substring.

Input: s = "ADOBECODEBANC", t = "X"

Output: ""

Explanation: The string "ADOBECODEBANC" does not contain the character 'X', so there is no valid window.

Time Complexity

O(m + n)

Space Complexity

O(m + n)