编写一个Java程序以按以下顺序打印：

Question

Input: {a, b, c, d} (Character Array)

I want to generate below sequence using above character array as Input

Output:

a bcd
ab cd
abc d
abcd
a b c d
ab c d
a bc d
a b cd

Answer 1

You can try,

char[] a = { 'a', 'b', 'c', 'd' };
        for (int i = 0; i < (a.length*2); i++) {
            if (i < a.length) {
                for (int j = 0; j < a.length; j++) {
                    System.out.print(a[j]);
                    if (j == i)
                        System.out.print(" ");
                }
                System.out.println("");
            } else {
                for (int k = 0; k < a.length; k++) {
                    System.out.print(a[k]);
                    if (k != (i - (a.length + 1)))
                        System.out.print(" ");
                }
                System.out.println("");
            }
        }

Answer 2

import org.apache.commons.lang3.StringUtils;

public class Demo2 {
  public static void main(String...args){

    char [] a = {'a','b','c','d'};
    String str = String.valueOf(a);//convert to 
    String[] input = str.split("");//string array 
    String str1 = StringUtils.join(input,""); // join to "abcd" for the first half of output
    String str2 = StringUtils.join(input," "); // join to "a b c d" for the second half of output
    for(int i = 1; i<str1.length()+1; i++){
        System.out.println(str1.substring(0, i)+" "+str1.substring(i, str1.length())); //insert " "at index i
    }
    System.out.println(str2);
    for(int i = 1; i<str2.length()-1; i=i+2){
        System.out.println(str2.substring(0, i)+""+str2.substring(i+1, str2.length())); //remove " " at index i
    }        
  }
}

Answer 3

for (int i = (1 << (a.length - 1)) - 1; i >= 0; --i) {
    System.out.print(a[0]);
    for (int j = 0; j < a.length - 1; ++j) {
        if ((i & (1 << j)) == 0)
            System.out.print(" ");
        System.out.print(a[j + 1]);
    }
    System.out.println();
}

Answer 4

this code works for the above given output,

 for(i=0;i<(2*a.length);i++){
        if(i<a.length){         
            for(j=0;j<a.length;j++){
            System.out.print(a[j]);
            if(j==i)
               System.out.print(" ");//for white spaces
        }
   System.out.println("");  //new line
   }
   else{
      for(k=0;k<a.length;k++){
         System.out.print(a[k]);
         if(k!=(i-(a.length+1)))
            System.out.print(" ");
      }   
   System.out.println("");  
   }
}

But, i think your code doesn't give the expected output, not even the first few lines as you said.