JavaAlgorithms/Searches/SaddlebackSearch.java

package Searches;

import java.util.Scanner;

/**
 * Program to perform Saddleback Search Given a sorted 2D array(elements are sorted across every row
 * and column, assuming ascending order) of size n*m we can search a given element in O(n+m)
 *
 * <p>we start from bottom left corner if the current element is greater than the given element then
 * we move up else we move right Sample Input: 5 5 ->Dimensions -10 -5 -3 4 9 -6 -2 0 5 10 -4 -1 1 6
 * 12 2 3 7 8 13 100 120 130 140 150 140 ->element to be searched output: 4 3 // first value is row,
 * second one is column
 *
 * @author Nishita Aggarwal
 */
public class SaddlebackSearch {

  /**
   * This method performs Saddleback Search
   *
   * @param arr The **Sorted** array in which we will search the element.
   * @param row the current row.
   * @param col the current column.
   * @param key the element that we want to search for.
   * @return The index(row and column) of the element if found. Else returns -1 -1.
   */
  private static int[] find(int arr[][], int row, int col, int key) {

    // array to store the answer row and column
    int ans[] = {-1, -1};
    if (row < 0 || col >= arr[row].length) {
      return ans;
    }
    if (arr[row][col] == key) {
      ans[0] = row;
      ans[1] = col;
      return ans;
    }
    // if the current element is greater than the given element then we move up
    else if (arr[row][col] > key) {
      return find(arr, row - 1, col, key);
    }
    // else we move right
    return find(arr, row, col + 1, key);
  }

  /**
   * Main method
   *
   * @param args Command line arguments
   */
  public static void main(String[] args) {
    // TODO Auto-generated method stub
    Scanner sc = new Scanner(System.in);
    int arr[][];
    int i, j, rows = sc.nextInt(), col = sc.nextInt();
    arr = new int[rows][col];
    for (i = 0; i < rows; i++) {
      for (j = 0; j < col; j++) {
        arr[i][j] = sc.nextInt();
      }
    }
    int ele = sc.nextInt();
    // we start from bottom left corner
    int ans[] = find(arr, rows - 1, 0, ele);
    System.out.println(ans[0] + " " + ans[1]);
    sc.close();
  }
}