【蓝桥杯Java_C组·从零开始卷】第六节(二)、蓝桥杯常用数学公式

package Action;

public class demo {
	/*
	 * 求最大公约数 最小公倍数 思路：根据欧几里得定理 gcd(a,b)=gcd(b,a%b);
	 */
	static int gcd(int a, int b) {
		// 出口：b=0;5和0的最大公约数是5
		if (b == 0)
			return a;
		return gcd(b, a % b);
	}

	static int lcm(int a, int b) {
		return a * b / gcd(a, b);
	}

	public static void main(String[] args) {
		System.out.println(gcd(45, 35));
		System.out.println(lcm(45, 35));
		System.out.println(gcd(42, 60));
		System.out.println(lcm(42, 60));
	}
}

package Action;

public class demo {
	public static void main(String[] args) {
		int max = 0;
		for (int i = 1; i <= 70044; i++) {
			if (70044 % i == 0 && 113148 % i == 0) {
				max = i;
			}
		}
		System.out.println(max);
	}
}

package Action;

import java.util.Scanner;

public class demo {
	public static void main(String[] args) {
		@SuppressWarnings("resource")
		Scanner sc = new Scanner(System.in);
		long n = sc.nextLong();
		if (n % 2 == 0) {
			if (n % 3 == 0) {
				long m = (n - 1) * (n - 2) * (n - 3);
				System.out.println(m);
			} else {
				long m = n * (n - 1) * (n - 3);
				System.out.println(m);
			}
		} else {
			long m = n * (n - 1) * (n - 2);
			System.out.println(m);
		}
	}
}

package Action;

import java.util.Scanner;

public class demo {
	public static void main(String[] args) {
		@SuppressWarnings("resource")
		Scanner sc = new Scanner(System.in);
		int a = sc.nextInt();
		int b = sc.nextInt();
		int c = sc.nextInt();
		double l = (a + b + c) * 1.0 / 2;
		double s = Math.sqrt(l * (l - a) * (l - b) * (l - c));
		System.out.println(String.format("%.2f", s));
	}
}

package Action;

public class demo {
	public static void main(String[] args) {
		//例如：有3小球，拿出一个小球有几种排列方法
		//p(n,m)=n!/(n-m)!
		int n=15;
		int m=3;
		System.out.println(jc(n)/(jc(n-m)));
	}
	//计算阶乘的递归使用方法
	public static int jc(int i) {
		if(i<=1) {
			return 1;
		}
		return i*jc(i-1);
	}
}