Question

I know that this question has been answered before on stackoverflow, however I am asking this not to tell me the correct code, but because I want to know what I am doing wrong.

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public static void printCombinations(String str){
    printCombinations(str, 0, str.length()-1);
}

public static void printCombinations(String str,int k,int n){
    if(k == n)
        System.out.println(str);
    else {
        for(int i=k;i<n;i++){
            String tmp=modifyString(str,i,k);
            printCombinations(tmp,k+1,n);
            modifyString(str,i,k);
        }
    }
}

public static String modifyString(String str,int x,int y){

            // for swapping characters inside a string 
    char arr[]=str.toCharArray();
    char t= arr[x];
    arr[x]=arr[y];
    arr[y]=t;

    String s= new String(arr);
    return s;   
}

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I am calling the function as printCombinations(s).

Answer 1

change

i<n to i<=n

it should work.