Minimum Window Substring
Given two strings s and t, 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 "".
Example:
ADOBECODEBANC ABC
BANC
- We start by creating a frequency map of the characters in string
t:A: 1, B: 1, C: 1. - Then, we iterate over string
sto find the minimum window substring that contains all characters int, using a sliding window approach to track the characters and their frequencies. - The minimum window substring is found to be
BANC, which contains all characters intwith the minimum length of 4 characters. - The final output is
BANC, as it is the smallest substring ofsthat includes every character int.
Constraints:
- 1 <= len(s), len(t) <= 10^5
- s and t consist of uppercase and lowercase English letters
Background Knowledge
The Minimum Window Substring problem involves finding the smallest substring of a given string s that contains all characters of another string t. This problem is a classic example of a sliding window problem, which is a common technique used in string and array problems. The sliding window approach involves creating a window that moves over the string, expanding or shrinking as necessary to meet certain conditions.
To understand this problem, it's essential to have a good grasp of string manipulation and hashing concepts. Hashing is particularly useful in this problem, as it allows us to efficiently keep track of the characters in the string t and their frequencies. We can use a hash map (or dictionary) to store the frequency of each character in t and then use this information to determine when we have found a valid window.
The problem also requires an understanding of optimization techniques, as we need to find the minimum window that satisfies the condition. This involves minimizing the size of the window while ensuring that it contains all the required characters. The greedy algorithm and two-pointer technique are also relevant concepts that can be applied to this problem.
Algorithm/Approach
The general approach to solving this problem involves using a sliding window technique, where we maintain a window of characters in the string s and expand or shrink it as necessary to include all characters of t. We can use a two-pointer technique to implement the sliding window, where one pointer represents the start of the window and the other represents the end.
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