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  //                 / /   / __ \/ __ `/ / ___/  |/ / / __                 //
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  //                                                                       //
  //               The Next Generation Logic Library                       //
  //                                                                       //
  ///////////////////////////////////////////////////////////////////////////
  //                                                                       //
  //  Copyright 2015-20xx Christoph Zengler                                //
  //                                                                       //
  //  Licensed under the Apache License, Version 2.0 (the "License");      //
  //  you may not use this file except in compliance with the License.     //
  //  You may obtain a copy of the License at                              //
  //                                                                       //
  //  http://www.apache.org/licenses/LICENSE-2.0                           //
  //                                                                       //
  //  Unless required by applicable law or agreed to in writing, software  //
  //  distributed under the License is distributed on an "AS IS" BASIS,    //
  //  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or      //
  //  implied.  See the License for the specific language governing        //
  //  permissions and limitations under the License.                       //
  //                                                                       //
  ///////////////////////////////////////////////////////////////////////////
  
  package org.logicng.collections;
  
  import java.util.Arrays;
  
  /**
   * A simple vector for integer elements implementation (inspired by MiniSat and CleaneLing).
   * <p>
   * In theory one could use the {@link LNGVector} also for integers.  But Java's auto-boxing comes with such a large
   * performance penalty that for the mission critical data structures of the SAT solvers we use this specialized
   * implementation.
   * @version 1.0
   * @since 1.0
   */
  public final class LNGIntVector {
  
      private int[] elements;
      private int size;
  
      /**
       * Creates a vector with an initial capacity of 5 elements.
       */
      public LNGIntVector() {
          this(5);
      }
  
      /**
       * Creates a vector with a given capacity.
       * @param size the capacity of the vector.
       */
      public LNGIntVector(final int size) {
          this.elements = new int[size];
      }
  
      /**
       * Creates a vector with a given capacity and a given initial element.
       * @param size the capacity of the vector
       * @param pad  the initial element
       */
      public LNGIntVector(final int size, final int pad) {
          this.elements = new int[size];
          Arrays.fill(this.elements, pad);
          this.size = size;
      }
  
      /**
       * Copy constructor.
       * @param other the other byte vector.
       */
      public LNGIntVector(final LNGIntVector other) {
          this.elements = Arrays.copyOf(other.elements, other.size);
          this.size = other.size;
      }
  
      /**
       * Creates a vector with the given elements.
       * @param elems the elements
       */
      public LNGIntVector(final int... elems) {
          this.elements = Arrays.copyOf(elems, elems.length);
          this.size = elems.length;
      }
  
      /**
       * Returns whether the vector is empty or not.
       * @return {@code true} if the vector is empty, {@code false} otherwise
       */
      public boolean empty() {
          return this.size == 0;
      }
  
      /**
       * Returns the size of the vector.
       * @return the size of the vector
       */
      public int size() {
          return this.size;
      }
  
      /**
       * Returns the last element of the vector and leaves it on the vector.
       * @return the last element of the vector
       */
      public int back() {
          return this.elements[this.size - 1];
      }
  
      /**
       * Pushes an element at the end of the vector.
       * @param element the element to push
       */
      public void push(final int element) {
          final int newSize = this.size + 1;
          this.ensure(newSize);
          this.elements[this.size++] = element;
      }
  
      /**
       * Pushes an element and assumes that there is enough space on the vector.
       * @param element the element to push
       * @throws ArrayIndexOutOfBoundsException if there was not enough space on the vector
       */
      public void unsafePush(final int element) {
          this.elements[this.size++] = element;
      }
  
      /**
       * Returns the element at a given position in the vector.
       * @param position the position
       * @return the element at the position
       * @throws ArrayIndexOutOfBoundsException if the position is not found in the vector
       */
      public int get(final int position) {
          return this.elements[position];
      }
  
      /**
       * Sets an element at a given position in the vector.
       * @param position the position
       * @param element  the element
       * @throws ArrayIndexOutOfBoundsException if the position is not found in the vector
       */
      public void set(final int position, final int element) {
          this.elements[position] = element;
      }
  
      /**
       * Removes the last element of the vector.
       */
      public void pop() {
          this.elements[--this.size] = -1;
      }
  
      /**
       * Shrinks the vector to a given size if the new size is less than the current size.  Otherwise, the size remains
       * the same.
       * @param newSize the new size
       */
      public void shrinkTo(final int newSize) {
          if (newSize < this.size) {
              this.size = newSize;
          }
      }
  
      /**
       * Grows the vector to a new size and initializes the new elements with a given value.
       * @param size the new size
       * @param pad  the value for new elements
       */
      public void growTo(final int size, final int pad) {
          if (this.size >= size) {
              return;
          }
          this.ensure(size);
          for (int i = this.size; i < size; i++) {
              this.elements[i] = pad;
          }
          this.size = size;
      }
  
      /**
       * Removes a given number of elements from the vector.
       * @param num the number of elements to remove.
       * @throws ArrayIndexOutOfBoundsException if the number of elements to remove is larger than the size of the vector
       */
      public void removeElements(final int num) {
          int count = num;
          while (count-- > 0) {
              this.elements[--this.size] = -1;
          }
      }
  
      /**
       * Clears the vector.
       */
      public void clear() {
          this.size = 0;
      }
  
      /**
       * Sorts this vector.
       */
      public void sort() {
          Arrays.sort(this.elements, 0, this.size);
      }
  
      /**
       * Sorts this vector in reverse order.
       */
      public void sortReverse() {
          Arrays.sort(this.elements, 0, this.size);
          for (int i = 0; i < this.size / 2; i++) {
              final int temp = this.elements[i];
              this.elements[i] = this.elements[this.size - i - 1];
              this.elements[this.size - i - 1] = temp;
          }
      }
  
      /**
       * Returns this vector's contents as an array.
       * @return the array
       */
      public int[] toArray() {
          return Arrays.copyOf(this.elements, this.size);
      }
  
      /**
       * Ensures that this vector has the given size.  If not - the size is doubled and the old elements are copied.
       * @param newSize the size to ensure
       */
      private void ensure(final int newSize) {
          if (newSize >= this.elements.length) {
              final int[] newArray = new int[Math.max(newSize, this.size * 2)];
              System.arraycopy(this.elements, 0, newArray, 0, this.size);
              this.elements = newArray;
          }
      }
  
      @Override
      public String toString() {
          final StringBuilder sb = new StringBuilder("[");
          for (int i = 0; i < this.size; i++) {
              sb.append(this.elements[i]);
              if (i != this.size - 1) {
                  sb.append(", ");
              }
          }
          sb.append("]");
          return sb.toString();
      }
  }
  