Algorithm to find substring within a string or a paragraph

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Finding substring
Often we come across interview questions like , find all occurances of a given substring within a string. What are the best possible strategies to solve this problem ? Well, there could be many but today in this blog I will consider explaining the simplest and most straightforawrd way of looking for a substring within a given string and it’s linear search (costly though, but this algorithm can be optimized). Below is a small C program that explains the solution to the above problem:
ID provided is not a Gistpen repo.
Below is the link to compile and execute the above code: Substring pattern match Let’s try to understand what the above program does: It has a nested loop. The outer loop loops through the given string parsing the string character by character. The inner loop parses the substring character by character and looking for a possible match of it’s first character to that of the current character of the main string. If the characters match, it does a stnrcmp() wherein it will compare N characters (N = length of substring) starting from current index and if a match is encountered, the index is pushed into the array. This iteration goes till the length of the main string. This algorithm can be further extended to create a find and replace functionality which will be the topic of my next blog. Stay tuned for more interesting stuff and please comment if there are any doubts in this one.  

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An avid reader, responsible for generating creative content ideas for golibrary.co. His interests include algorithms and programming languages. Blogging is a hobby and passion.

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