Minimum Window Substring
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 an empty string.
If there is such a substring, it is guaranteed to be unique.
Example 1
Input
ADOBECODEBANC ABC
Output
BANC
Explanation
The substring "BANC" is the smallest window that contains all the characters 'A', 'B', and 'C'.
Example 2
Input
a a
Output
a
Explanation
The entire string itself is the minimum window containing all characters of t.
Constraints
Hints:
Hint 1
Count the frequency of each character required from t.
Hint 2
Use a sliding window. Expand the right pointer until all required characters are present, then shrink the left pointer while maintaining validity to obtain the smallest window.
Author & Technical Reviewer
Technically reviewed by: ExamAdda Technical Review Team
Technical Reviewers, ExamAdda
Software engineers at ExamAdda who check every article's definitions, complexity claims and code examples before and after publishing.
Published
Aug 5, 2026
Last updated
Aug 6, 2026
Content Verification Methodology
Definitions and complexity claims were checked against authoritative computer-science references. Code examples were compiled and tested with standard, boundary and edge-case inputs.
Expected Output