Given an input string and a pattern, check if characters in the input string follows the same order as determined by characters present in the pattern. Assume there won’t be any duplicate characters in the pattern.
Input: string = "engineers rock" pattern = "er"; Output: true Explanation: All 'e' in the input string are before all 'r'. Input: string = "engineers rock" pattern = "egr"; Output: false Explanation: There are two 'e' after 'g' in the input string. Input: string = "engineers rock" pattern = "gsr"; Output: false Explanation: There are one 'r' before 's' in the input string.
The idea is very simple. For every pair (x, y) of consecutive characters in the pattern string, we find the last occurrence of x and first occurrence of y in the input string. If last occurrence of character x is after first occurrence of character y for any pair, we return false. Checking for every pair of consecutive characters in the pattern string will suffice. For example, if we consider three consecutive characters in the pattern say x, y and z, if (x, y) and (y, z) returns true, that implies (x, z) is also true.
Below is the implementation of above idea –
We have discussed two more approaches to solve this problem.
Check if string follows order of characters defined by a pattern or not | Set 2
Check if string follows order of characters defined by a pattern or not | Set 3
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