iOS

Sort Characters By Frequency

[Questions]: Given a string s, sort it in decreasing order based on the frequency of the characters. for example “tree” so ee has highest appearance hence answer will be eert Return the sorted string. If there are multiple answers, return any of themInput: s = “tree”Output: “eert”

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How to check Isomorphic Strings?

[Question]: Given two strings s and t, determine if they are isomorphic. Definition: Two strings s and t are isomorphic if the characters in s can be replaced to get t. All occurrences of a character must be replaced with another character while preserving the order of characters. No two characters may map to the same character, but a character may map to itself. Example 1:

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Check if string is rotated

[Question]: Given two strings s and goal, return true if and only if s can become goal after some number of shifts on s. A shift on s consists of moving the leftmost character of s to the rightmost position. For example, if s = “abcde”, then it will be “bcdea” after one shift. Input: s = “abcde”, goal = “abced” Output: false

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