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challenge_3.js
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57 lines (53 loc) · 1001 Bytes
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function isPrime(n) {
var i = 2
, sqrt_n = Math.sqrt(n)
;
while (i < sqrt_n) {
if (n % i === 0 ) {
return false;
}
i += 1;
}
return true;
}
function isPallindrome(n) {
var digits = ""
, digits_len = 0
, half_digits = 0
, i = 0
;
if (typeof(n) !== 'number') {
return false;
}
digits = n.toString().split("");
digits_len = digits.length;
if ( digits_len === 0 ) {
return false;
} else if ( digits_len === 1) {
return true;
} else if (digits_len === 2 ) {
return digits[0] === digits[1];
} else {
half_digits = Math.floor(digits_len/2);
do {
if (digits[i] !== digits[ digits_len - i - 1 ]) {
return false;
}
i += 1;
} while( i < half_digits ) ;
}
return true;
}
function driver(n) {
var last_pp = 0
, i = 2
;
do {
if (isPrime(i) && isPallindrome(i) ) {
last_pp = i;
}
i += 1;
} while (i < n);
return last_pp;
}
console.log( driver(1000) );