Search a 2D Matrix II

Write an efficient algorithm that searches for a value in an m x n 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.

For example,

Consider the following matrix:

  1. [
  2.   [1,   4,  7, 11, 15],
  3.   [2,   5,  8, 12, 19],
  4.   [3,   6,  9, 16, 22],
  5.   [10, 13, 14, 17, 24],
  6.   [18, 21, 23, 26, 30]
  7. ]

Given target = 5, return true.

Given target = 20, return false.

Solution:

  1. public class Solution {
  2.   public boolean searchMatrix(int[][] matrix, int target) {
  3.     int n = matrix.length, m = matrix[0].length;
  5.     int i = 0, j = m - 1;
  7.     while (i < n && j >= 0) {
  8.       if (matrix[i][j] == target)
  9.         return true;
  11.       if (target < matrix[i][j])
  12.         j--;
  13.       else
  14.         i++;
  15.     }
  17.     return false;
  18.   }
  19. }