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Added string pattern matching algorithm #238

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Merged
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Aug 19, 2020
Merged

Added string pattern matching algorithm #238

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36 changes: 36 additions & 0 deletions String/PatternMatching.js
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Original file line number Diff line number Diff line change
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/*
Pattern matching is case insensitive as
the inputs are converted to lower case before the
algorithm is run.

The algorithm will run through the entire text and
return the starting index if the given pattern is
available in the text
*/
const checkIfPatternExists = (text, pattern) => {
const textLength = text.length // Store the length of the text in a variable
const patternLength = pattern.length // Store the length of the pattern in a variable

// Iterate through the text until the textlength - patternlength index
for (let i = 0; i <= textLength - patternLength; i++) {
// For each character in the text check if the subsequent character
// are matching the given pattern; if not break from the condition
for (let j = 0; j < textLength; j++) {
if (text[i + j] !== pattern[j]) break

// For each iteration of j check if the value of
// j + 1 is equal to the length of the pattern
if (j + 1 === patternLength) {
console.log(`Given pattern is found at index ${i}`)
}
}
}
}

const main = () => {
const text = 'AABAACAADAABAAAABAA'
const pattern = 'AABA'
checkIfPatternExists(text.toLowerCase(), pattern.toLowerCase())
}

main()