下一个质数 Java 仅适用于某些数字 [英] Next Prime number Java only working with certain numbers

问题描述

此功能仅适用于某些数字，但对于 15 或 5，它不能给我正确的下一个素数.

This function its only working for certain numbers, but for 15, or 5 it does not give me correct next prime.

public static int nextPrime(int n) {
    boolean isPrime = false;
    int m = (int) Math.ceil(Math.sqrt(n));
    int start = 3;
    if (n % 2 == 0) {
        n = n + 1;
    }
    while (!isPrime) {
        isPrime = true;
        for (int i = start; i <= m; i = i + 2) {
            if (n % i == 0) {
                isPrime = false;
                break;
            }
        }
        if (!isPrime) {
            n = n + 2;
        }
    }
    return n;
}

推荐答案

你不需要去到sqrt(n)，你需要去到你正在评估的sqrt(number)

You don't need to go upto sqrt(n), you need to go upto sqrt(number) that you are evaluating

例如考虑您通过 n = 5

for example consider you pass n = 5

它将从 3 开始循环，并在 4 结束循环，这不是您找到下一个质数所需的

it will start loop from 3 and it will end the loop at 4 that is not what you need to find next prime number

外循环从 n + 1 开始，直到找到素数内循环你应该从 3 和 sqrt(numberUnderIteration) 开始

outer loop start from n + 1 until you find prime inner loop you should start from 3 and sqrt(numberUnderIteration)

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