Search_a_2D_Matrix_II.java

/*

Write an efficient algorithm that searches for a value target in an m x n integer matrix matrix. This matrix has the following properties:

Integers in each row are sorted in ascending from left to right.
Integers in each column are sorted in ascending from top to bottom.
 

Example 1:


Input: matrix = [[1,4,7,11,15],[2,5,8,12,19],[3,6,9,16,22],[10,13,14,17,24],[18,21,23,26,30]], target = 5
Output: true
Example 2:


Input: matrix = [[1,4,7,11,15],[2,5,8,12,19],[3,6,9,16,22],[10,13,14,17,24],[18,21,23,26,30]], target = 20
Output: false
 

Constraints:

m == matrix.length
n == matrix[i].length
1 <= n, m <= 300
-109 <= matrix[i][j] <= 109
All the integers in each row are sorted in ascending order.
All the integers in each column are sorted in ascending order.
-109 <= target <= 109

*/

class Search_a_2D_Matrix_II {
    public boolean searchMatrix(int[][] matrix, int target) {
        int n = matrix.length;
        int m = matrix[0].length;
        // Taking a corner element
        // Taking the element "18" to start with
        int row = n-1; 
        int col = 0; 
        while(row >= 0 && col < m){
            if (matrix[row][col]== target){
                return true;
            }
            else if (matrix[row][col] > target){
                row --;
            }
            else{
                col ++;
            }
        }
        return false;
    }
}