java代码排列组合

// 排列组合
public class Main {
    static Stack<Integer> stack = new Stack<>();
    public static void main(String[] args) {
        int shu[] = {1,2,3,4};
        f(shu,4,0);
    }
    /**
     * @param shu   待选择的数组
     * @param targ  要选择多少个次
     * @param cur   当前选择的是第几次
     */
    private static void f(int[] shu, int targ, int cur) {
        if (targ==cur){
            System.out.println(stack);
            return;
        }
        for (int i = 0; i < shu.length; i++) {
            if (!stack.contains(shu[i])){
                stack.add(shu[i]);
                f(shu,targ,cur+1);
                stack.pop();
            }
        }
    }
}

结果:

[1, 2, 3, 4]
[1, 2, 4, 3]
[1, 3, 2, 4]
[1, 3, 4, 2]
[1, 4, 2, 3]
[1, 4, 3, 2]
[2, 1, 3, 4]
[2, 1, 4, 3]
[2, 3, 1, 4]
[2, 3, 4, 1]
[2, 4, 1, 3]
[2, 4, 3, 1]
[3, 1, 2, 4]
[3, 1, 4, 2]
[3, 2, 1, 4]
[3, 2, 4, 1]
[3, 4, 1, 2]
[3, 4, 2, 1]
[4, 1, 2, 3]
[4, 1, 3, 2]
[4, 2, 1, 3]
[4, 2, 3, 1]
[4, 3, 1, 2]
[4, 3, 2, 1]

分析过程: