主要因素和 JavaScript [英] Prime factor and JavaScript
问题描述
我被我用来解决一个问题的 JavaScript 代码困住了:
I'm stuck with the JavaScript code I am using for solving a problem which states:
13195 的质因数是 5、7、13 和 29.600851475143 的最大质因数是多少?
The prime factors of 13195 are 5, 7, 13 and 29. What is the largest prime factor of the number 600851475143 ?
(这不是家庭作业，是在线编码/数学挑战)
(this is not homework, is an online coding/mathematical challenge)
所以我想出了这个解决方案:
So I came up with this solution:
<html>
<head>
<script type="text/javascript">
// This function checks whether it's possible to divide the prime number
function al(n){
// k = 13195 is the number that I have to find the prime factor for
var k = 13195;
if (k%n) {
return;
}
else {
document.write(n + ' ');
}
}
</script>
</head>
<body>
<script type="text/javascript">
//a and b are just for counting from the number n to 2 to find the prime numbers
var a = 2;
for (var n = 13194 ; n>a ; n--) {
var b = 2;
//if the found number is divisible, we skip it
while(b<n) {
if (n % b == 0) {
break;
}
else if (b = n - 1){
al(n);
}
b++;
}
}
</script>
</body>
</html>
现在问题来了:这会输出这些数字:2639 1885 1015 455 377 203 145 91 65 35 29 13 7 5".这些不是质数.我查看了数字，发现数字 13195 除以 5(最后一个数字)给出了第一个数字；2639;13195 除以 7 得到 1885；等
Now to the problem: This outputs these numbers: "2639 1885 1015 455 377 203 145 91 65 35 29 13 7 5". These aren't prime numbers. I've looked at the numbers and I found that the number 13195 divided by 5 (the last number) gives the first number; 2639; 13195 divided by 7 gives 1885; etc.
我到底做错了什么?
推荐答案
您的问题不是数学问题 -- 您只是在条件检查中遇到了错误.
Your issue isn't a mathematical one -- you just have a bug in one of your conditional checks.
将if(b = n-1)改为if(b == n-1).现在，您的代码实际上并未进行检查以确保因子是质数；相反，它将 n-1 的值分配给 b(对于 n 的奇数值)，然后自动调用 a1(b)，所以你的结果是 k 的所有可能的奇数因子.
Change if(b = n-1) to if(b == n-1). Right now, your code isn't actually checking to ensure that a factor is prime; instead, it's assigning the value of n-1 to b (for odd values of n) and then automatically calling a1(b), so your result is all possible odd factors of k.
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