【九度OJ】题目1439：Least Common Multiple 解题报告

标签（空格分隔）： 九度OJ

---

原题地址：http://ac.jobdu.com/problem.php?pid=1439

题目描述：

The least common multiple (LCM) of a set of positive integers is the smallest positive integer which is divisible by all the numbers in the set. For example, the LCM of 5, 7 and 15 is 105.

输入：

Input will consist of multiple problem instances. The first line of the input will contain a single integer indicating the number of problem instances. Each instance will consist of a single line of the form m n1 n2 n3 … nm where m is the number of integers in the set and n1 … nm are the integers. All integers will be positive and lie within the range of a 32-bit integer.

输出：

For each problem instance, output a single line containing the corresponding LCM. All results will lie in the range of a 32-bit integer.

样例输入：

23 5 7 156 4 10296 936 1287 792 1

样例输出：

10510296

Ways

BigInteger类好！

这个题的意思很简单，其实就是求指定数字的最小公倍数。

我们可以利用上一题的经验，求出m个数的共同最小公倍数即可。

做题时一个错误的地方就是注意两层循环的嵌套，把循环变量给写错了，导致一直出错。

import java.util.*;import java.math.*;public class Main{    public static void main(String[] args) {        Scanner scanner = new Scanner(System.in);        String n = scanner.nextLine();        for (int i = 0; i < Integer.parseInt(n); i++) {            String line = scanner.nextLine();            String[] params = line.split(" ");            BigInteger a = new BigInteger(params[1]);            for (int j = 2; j < params.length; j++) {                BigInteger b = new BigInteger(params[j]);//是j，不是i                a = a.multiply(b).divide(a.gcd(b));            }            System.out.println(a.toString());        }    }}

本来以为C++的版本也会同样的容易，可是还是遇到点问题，很不爽。原因是因为结果超出了int范围。改成long long就好了。

#include <stdio.h>long long gcd(long long a, long long b) {    return b != 0 ? gcd(b, a % b) : a;}int main() {    int n;    while (scanf("%d", &n) != EOF) {        while (n-- != 0) {            int m;            scanf("%d", &m);            long long answer = 1;            while (m-- != 0) {                int temp;                scanf("%d", &temp);                answer = answer * temp / gcd(answer, temp);            }            printf("%lld\n", answer);        }    }    return 0;}

Date

2017 年 3 月 7 日