50 lines
2.0 KiB
Java
50 lines
2.0 KiB
Java
/*
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Backtracking algorithm used in the program:-
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>>Fix a character in the first position and swap the rest of the character with the first character.
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Like in ABC, in the first iteration three strings are formed: ABC, BAC, and CBA by swapping A with
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A, B and C respectively.
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>>Repeat step 1 for the rest of the characters like fixing second character B and so on.
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>>Now swap again to go back to the previous position. E.g., from ABC, we formed ABC by fixing B again,
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and we backtrack to the previous position and swap B with C. So, now we got ABC and ACB.
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>>Repeat these steps for BAC and CBA, to get all the permutations.
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*/
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public class PermuteString {
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//Function for swapping the characters at position I with character at position j
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public static String swapString(String a, int i, int j) {
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char[] b =a.toCharArray();
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char ch;
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ch = b[i];
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b[i] = b[j];
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b[j] = ch;
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return String.valueOf(b);
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}
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public static void main(String[] args)
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{
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String str = "ABC";
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int len = str.length();
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System.out.println("All the permutations of the string are: ");
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generatePermutation(str, 0, len);
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}
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//Function for generating different permutations of the string
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public static void generatePermutation(String str, int start, int end)
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{
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//Prints the permutations
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if (start == end-1)
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System.out.println(str);
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else
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{
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for (int i = start; i < end; i++)
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{
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//Swapping the string by fixing a character
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str = swapString(str,start,i);
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//Recursively calling function generatePermutation() for rest of the characters
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generatePermutation(str,start+1,end);
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//Backtracking and swapping the characters again.
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str = swapString(str,start,i);
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}
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}
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}
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} |