240.search-a-2-d-matrix-ii.java

/*
 * @lc app=leetcode id=240 lang=java
 *
 * [240] Search a 2D Matrix II
 *
 * https://leetcode.com/problems/search-a-2d-matrix-ii/description/
 *
 * algorithms
 * Medium (41.27%)
 * Likes:    1722
 * Dislikes: 50
 * Total Accepted:    200.2K
 * Total Submissions: 484.8K
 * Testcase Example:  '[[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]]\n5'
 *
 * 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.
 *
 *
 * Example:
 *
 * Consider the following 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]
 * ]
 *
 *
 * Given target = 5, return true.
 *
 * Given target = 20, return false.
 *
 */
class Solution {
  public boolean searchMatrix(int[][] matrix, int target) {
    if (matrix == null || matrix.length == 0 || matrix[0].length == 0) {
      return false;
    }

    int rowMax = matrix.length - 1;
    int colMax = matrix[0].length - 1;
    int rowCur = 0;
    int colCur = colMax;

    while (rowCur <= rowMax && colCur >= 0) {
      if (matrix[rowCur][colCur] == target) {
        return true;
      } else if (matrix[rowCur][colCur] > target) {
        colCur--;
      } else {
        rowCur++;
      }
    }

    return false;
  }
}