content: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You 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.apache.arrow.algorithm.search;
  
  import org.apache.arrow.algorithm.sort.VectorValueComparator;
  import org.apache.arrow.vector.ValueVector;
  
  /** Search for a particular element in the vector. */
  public final class VectorSearcher {
  
    /** Result returned when a search fails. */
    public static final int SEARCH_FAIL_RESULT = -1;
  
    /**
     * Search for a particular element from the key vector in the target vector by binary search. The
     * target vector must be sorted.
     *
     * @param targetVector the vector from which to perform the sort.
     * @param comparator the criterion for the sort.
     * @param keyVector the vector containing the element to search.
     * @param keyIndex the index of the search key in the key vector.
     * @param <V> the vector type.
     * @return the index of a matched element if any, and -1 otherwise.
     */
    public static <V extends ValueVector> int binarySearch(
        V targetVector, VectorValueComparator<V> comparator, V keyVector, int keyIndex) {
      comparator.attachVectors(keyVector, targetVector);
  
      // perform binary search
      int low = 0;
      int high = targetVector.getValueCount() - 1;
  
      while (low <= high) {
        int mid = low + (high - low) / 2;
        int cmp = comparator.compare(keyIndex, mid);
        if (cmp < 0) {
          high = mid - 1;
        } else if (cmp > 0) {
          low = mid + 1;
        } else {
          return mid;
        }
      }
      return SEARCH_FAIL_RESULT;
    }
  
    /**
     * Search for a particular element from the key vector in the target vector by traversing the
     * vector in sequence.
     *
     * @param targetVector the vector from which to perform the search.
     * @param comparator the criterion for element equality.
     * @param keyVector the vector containing the element to search.
     * @param keyIndex the index of the search key in the key vector.
     * @param <V> the vector type.
     * @return the index of a matched element if any, and -1 otherwise.
     */
    public static <V extends ValueVector> int linearSearch(
        V targetVector, VectorValueComparator<V> comparator, V keyVector, int keyIndex) {
      comparator.attachVectors(keyVector, targetVector);
      for (int i = 0; i < targetVector.getValueCount(); i++) {
        if (comparator.compare(keyIndex, i) == 0) {
          return i;
        }
      }
      return SEARCH_FAIL_RESULT;
    }
  
    private VectorSearcher() {}
  }
  