面试题—有重复序列全排列问题

Posted 2022-11-17 JeemyJohn

最近面试遇到个高频面试题：有重复序列全排列问题，现在Java代码展示给大家，原理稍后有空补充。

public class Demo 
    public static void main(String[] args) 
        char a1[] = 'a', 'b', 'c';
        perm(a1, 0, 3);

        System.out.println();

        char a2[] = 'a', 'b', 'b', 'c';
        perm(a2, 0, 4);
    

    /**
     * 判断是否有重复，有重复则在递归的过程中过滤
     */
    public static boolean isSwap(char s[], int start, int end) 
        for (int i = start; i < end; i++) 
            if (s[i] == s[end]) 
                return false;
            
        
        return true;
    

    /**
     * 交换数组元素
     */
    public static void swap(char s[], int i, int j) 
        char temp = s[i];
        s[i] = s[j];
        s[j] = temp;
    

    /**
     * 递归求全排列
     */
    public static void perm(char s[], int start, int end) 
        if (start == end) 
            for (int i = 0; i < end; i++) 
                System.out.print(s[i]);
            
            System.out.println();
         else 
            for (int i = start; i < end; i++) 
                if (isSwap(s, start, i)) 
                    swap(s, i, start);
                    perm(s, start + 1, end);
                    swap(s, i, start);