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January 18, 2017 21:29
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Checking if a number is a palindrome, without converting to a string. Demo at http://jsbin.com/panukukeda/edit?js,console
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| function getNthDigit(val, n) | |
| { | |
| var modVal = val % Math.pow(10,n);//Remove all digits larger than nth | |
| return Math.floor(modVal / Math.pow(10,n-1));//Remove all digits less than nth | |
| } | |
| /** | |
| * @param {number} x | |
| * @return {boolean} | |
| */ | |
| var isPalindrome = function(x) { | |
| var result = true; | |
| var length = Math.log(x) * Math.LOG10E + 1 | 0; | |
| if (x < 0) { | |
| result = false; | |
| } | |
| else if (length === 2 && x !== 11) { | |
| result = false; | |
| } | |
| else { | |
| for (var i=0; i<Math.ceil(length / 2); i++) { | |
| var d1 = getNthDigit(x, i + 1); | |
| var d2 = getNthDigit(x, length - i); | |
| if (d1 != d2) { | |
| result = false; | |
| break; | |
| } | |
| } | |
| } | |
| return result; | |
| }; |
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