Search a 2D Matrix

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 from left to right.
  • The first integer of each row is greater than the last integer of the previous row.

For example,

Consider the following matrix:

  1. [
  2.   [1,   3,  5,  7],
  3.   [10, 11, 16, 20],
  4.   [23, 30, 34, 50]
  5. ]

Given target = 3, return true.

Solution:

  1. public class Solution {
  2.   public boolean searchMatrix(int[][] matrix, int target) {
  3.     int n = matrix.length;
  4.     int m = matrix[0].length;
  6.     int i = 0;
  7.     int j = m - 1;
  9.     while (i < n && j >= 0) {
  10.       if (target == matrix[i][j]) {
  11.         return true;
  12.       }
  14.       if (target < matrix[i][j]) {
  15.         j--;
  16.       } else {
  17.         i++;
  18.       }
  19.     }
  21.     return false;
  22.   }
  23. }