Anagram Substring Detection

You are given two strings: a pattern string and a text string. Your task is to determine whether any rearrangement (anagram) of the pattern exists as a contiguous substring within the text.

An anagram of a string is another string that contains the exact same characters with the exact same frequencies, but potentially arranged in a different order. For example, "abc", "bca", and "cab" are all anagrams of each other.

Return true if the text contains at least one contiguous substring that is an anagram of the pattern. Return false otherwise.

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Understanding the Problem

Consider the pattern "ab" and the text "eidbaooo":

• The text contains the substring "ba" (at positions 3-4), which is an anagram of "ab"
• Since we found a valid anagram substring, we return true

Now consider the pattern "ab" and the text "eidboaoo":

• Examining all substrings of length 2: "ei", "id", "db", "bo", "oa", "ao", "oo"
• None of these are anagrams of "ab" (none contain exactly one 'a' and one 'b' adjacent to each other)
• Since no valid anagram substring exists, we return false

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Key Insight

The core insight is that you don't need to generate all permutations of the pattern (which would be factorial in complexity). Instead, two strings are anagrams if and only if they have identical character frequency distributions. This transforms the problem into efficiently comparing character frequencies across a sliding window.