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Arrays: Left Rotation

  • hackerrank_com23 + 3 comments

    Here's my in-place function implementation:

    public static int[] arrayLeftRotation(int[] a, int n, int k) {
    // Rotate in-place
    int[] temp = new int[k];
    System.arraycopy(a, 0, temp, 0, k);
    System.arraycopy(a, k, a, 0, n - k);
    System.arraycopy(temp, 0, a, n - k, k);
    return a;
}
    • Angi29 + 0 comments
      [deleted]
    • Angi29 + 0 comments

      idem, just a little variation : kifs

      static int[] rotLeft(int[] a, int d) {
    int length = a.length;
    int[] b = new int[length];

    System.arraycopy(a, d, b, 0, length - d);
    System.arraycopy(a, 0, b, length - d, d);
    return b;
}
    • denis631 + 1 comment

      How is this in-place when you allocate a new array of size k.

      • venom1724 + 0 comments

        Indeed, its not in-place at all. Also its slow. If you are interested, here's an inplace c++ solution 

        void rotLeft(vector<int> &a, int d) {
    int c=a[d],ci=0,n=a.size(); a[d]=0;
    for(int i=n-1;i>=0;i--){
        swap(a[ci],c);
        if(!c&&i) ci+=n-i+++i;
        ci=(n+ci-d)%n;
    }
}