Coding Question 5 Free Section

Program to Print all Permutations of a String

C

// C program to print all permutations with duplicates allowed
#include <stdio.h>
#include <string.h>

/* Function to swap values at two pointers */
void swap(char *x, char *y)
{
char temp;
temp = *x;
*x = *y;
*y = temp;
}

/* Function to print permutations of string
This function takes three parameters:
1. String
2. Starting index of the string
3. Ending index of the string. */
void permute(char *a, int l, int r)
{
int i;
if (l == r)
printf("%s\n", a);
else
{
for (i = l; i <= r; i++)
{
swap((a+l), (a+i));
permute(a, l+1, r);
swap((a+l), (a+i)); //backtrack
}
}
}

/* Driver program to test above functions */
int main()
{
char str[] = "ABC";
int n = strlen(str);
permute(str, 0, n-1);
return 0;
}

Java

package com.java2novice.algo;
 
import java.util.ArrayList;
import java.util.List;
 
public class StringPermutationsEx {
 
    public static void main(String a[]) {
 
        List<String> output = StringPermutationsEx.generatePermutations("xyz");
        System.out.println("Result size: "+output.size());
        output.stream().forEach(System.out::println);
        System.out.println("------------------");
 
        output = StringPermutationsEx.generatePermutations("ABCD");
        System.out.println("Result size: "+output.size());
        output.stream().forEach(System.out::println);
    }
 
    public static List<String> generatePermutations(String input) {
 
        List<String> strList = new ArrayList<String>();
        StringPermutationsEx.permutations("", input, strList);
 
        return strList;
    }
 
    private static void permutations(String consChars, String input, List<String> opContainer) {
 
        if(input.isEmpty()) {
            opContainer.add(consChars+input);
            return;
        }
 
        for(int i=0; i<input.length(); i++) {
            permutations(consChars+input.charAt(i),
                            input.substring(0, i)+input.substring(i+1),
                            opContainer);
        }
    }
}