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August 29, 2017 17:27
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Check if a string is a palindrome or not? - Another Efficient Method
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function palindrome(str) { | |
//assign a front and a back pointer | |
let front = 0; | |
let back = str.length - 1; | |
//back and front pointers won't always meet in the middle, so use (back > front) | |
while (back > front) { | |
//increments front pointer if current character doesn't meet criteria | |
while ( str[front].match(/[\W_]/) ) { | |
front++; | |
continue; | |
} | |
//decrements back pointer if current character doesn't meet criteria | |
while ( str[back].match(/[\W_]/) ) { | |
back--; | |
continue; | |
} | |
//finally does the comparison on the current character | |
if ( str[front].toLowerCase() !== str[back].toLowerCase() ) return false | |
front++; | |
back--; | |
} | |
//if the whole string has been compared without returning false, it's a palindrome! | |
return true; | |
} | |
console.log(palindrome("race car")); |
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