java：全排列

java沒有next_permutation()這個函數，需要自己寫。

import java.util.*;

public class Main {
	static Scanner sc = new Scanner(System.in);
	static int a[] = new int[15];
	// 交換函數
	static void swap(int x, int y) {
		int tmp = a[x];
		a[x] = a[y];
		a[y] = tmp;
	}
	// 求全排列
	static void permutation(int begin, int end) {
		if(begin > end) {
			for(int i = 1; i <= end; i++)
				System.out.print(a[i]);
			System.out.println();
			return ;
		}
		for(int i = begin; i <= end; i++) {
			swap(begin, i);
			permutation(begin + 1, end);
			swap(begin, i);
		}
	}
	// 將[begin, end]範圍內的數按升序排列
	static void reverse(int begin, int end) {
		while(begin < end) {
			swap(begin, end);
			begin++;
			end--;
		}
	}
	// 尋找下一個比當前序列大的序列
	static boolean next_permutation(int begin, int end) {
		int i = end;
		while(i > begin && a[i - 1] >= a[i]) i--;
		if(i == begin) return false;
		i--;
		int j = end;
		while(j > i && a[j] <= a[i]) j--;
		swap(i, j);
		reverse(i + 1, end);
		return true;
	}
	public static void main(String[] args) {
		int n;
		n = sc.nextInt();
		for(int i = 1; i <= n; i++)
			a[i] = sc.nextInt();
		do {
			for(int i = 1; i <= n; i++)
				System.out.print(a[i]);
			System.out.println();
		} while (next_permutation(1, n));
		System.out.println("全排列如下：");
		Arrays.sort(a, 1, n + 1);
		permutation(1, n);
	}
}