Determine the fewest character replacements needed to transform one string into an anagram of another. Essentially, find the minimum steps to make two strings have the same character frequencies.

Find the smallest substring within a larger string that contains all the characters of a target string. You need to locate the minimum window that satisfies this condition.

Find the length of the longest 'mountain' (increasing then decreasing sequence) within an array of numbers. The mountain must have at least 3 elements.