前几天去一家公司,看到一道面试题:求给定个数的质数之和,如F(3)=2+3+5=10,自己测试的代码如下
public class Test { /** * @Description Get after a specified number of the first prime Numbers * @param num a specified number * @return int * @throws */ public int getAfterSpecifiedNumOfTheFirstPrimeNum(int num) { int beginNum = num; if (beginNum == 0) { beginNum = 1; } for (int i = (beginNum + 1);; i++) { if (isPrimeNum(i)) { return i; } } } /** * @Description 判断一个数是否为质数 * @param num * @return boolean * @throws */ private boolean isPrimeNum(int num) { if (num < 2) { return false; } for (int i = 1; i < num; i++) { if (num % i == 0 && i != 1) { return false; } } return true; } /** * @Description 求指定个数质数的和 * @param num * @return int */ public int getContPrimeNum(int num) { int sum = 0; int primeNum = 0; for (int i = 0; i < num; i++) { primeNum = getAfterSpecifiedNumOfTheFirstPrimeNum(primeNum); sum += primeNum; } return sum; } public static void main(String[] args) { Test t = new Test(); System.out.println(t.getContPrimeNum(7)); } }