# Python | Check order of character in string using OrderedDict( )

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.

Examples:

```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.
```

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

We have existing solution for this problem, please refer Check if string follows order of characters defined by a pattern or not | Set 1. Here we solve this problem quickly in python using OrderedDict(). Approach is very simple,

• Create an OrderedDict of input string which contains characters of input strings as Key only.
• Now set a pointer at the start of pattern string.
• Now traverse generated OrderedDict and match keys with individual character of pattern string, if key and character matches with each other then increment pointer by 1.
• If pointer of pattern reaches it’s end that means string follows order of characters defined by a pattern otherwise not.

 `# Function to check if string follows order of  ` `# characters defined by a pattern ` `from` `collections ``import` `OrderedDict ` ` `  `def` `checkOrder(``input``, pattern): ` `     `  `    ``# create empty OrderedDict ` `    ``# output will be like {'a': None,'b': None, 'c': None} ` `    ``dict` `=` `OrderedDict.fromkeys(``input``) ` ` `  `    ``# traverse generated OrderedDict parallel with ` `    ``# pattern string to check if order of characters  ` `    ``# are same or not ` `    ``ptrlen ``=` `0`  `    ``for` `key,value ``in` `dict``.iteritems(): ` `        ``if` `(key ``=``=` `pattern[ptrlen]): ` `            ``ptrlen ``=` `ptrlen ``+` `1` `         `  `        ``# check if we have traverse complete  ` `        ``# pattern string ` `        ``if` `(ptrlen ``=``=` `(``len``(pattern))): ` `            ``return` `'true'` ` `  `    ``# if we come out from for loop that means  ` `    ``# order was mismatched ` `    ``return` `'false'` `  `  `# Driver program ` `if` `__name__ ``=``=` `"__main__"``: ` `    ``input` `=` `'engineers rock'`  `    ``pattern ``=` `'egr'` `    ``print` `checkOrder(``input``,pattern) `

Output:

```true
```

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