寻找完全数(从1开始到小于本身的所有约数之和,即完全约数的和)

//A.java

public class A {

	public static void main(String[] args) {
		for (int i = 2; i < 10000; i++) {
			if (isPerfect(i)) {
				System.out.print(i + " = ");
				exec(i);
			}
		}
	}

	public static boolean isPerfect(int n) {
		if (n == sum(n)) {
			return true;
		}
		return false;
	}

	public static int sum(int n) {
		int s = 1, i = 2;
		while (i < n / i) {
			if (n % i == 0) {
				s += (i + n / i);
			}
			i++;
		}
		return s;
	}

	public static void exec(int n) {
		System.out.print("1");
		int i = 2;
		while (i < n / i) {
			if (n % i == 0) {
				System.out.print(" + " + i + " + " + n / i);
			}
			i++;
		}
		System.out.println();
	}
}

 

运行结果：

 

6 = 1 + 2 + 3
28 = 1 + 2 + 14 + 4 + 7
496 = 1 + 2 + 248 + 4 + 124 + 8 + 62 + 16 + 31
8128 = 1 + 2 + 4064 + 4 + 2032 + 8 + 1016 + 16 + 508 + 32 + 254 + 64 + 127