74. 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.Example 1:Input:matrix = [ [1, 3, 5, 7], [10, 11, 16, 20], [23, 30, 34, 50]]target = 3Output: trueExample 2:Input:matrix = [ [1, 3, 5, 7], [10, 11, 16, 20], [23, 30, 34, 50]]target = 13Output: false难度：medium题目：写算法在m * n的矩阵中查找给定的值。矩阵特征如下：矩阵中的每行升序排列。每行中的的第一个数大于其前一行的最后一个数。思路：从最后一列中找出第一个大于target的值，并记录下当前行。然后对该行进行二分查找。Runtime: 5 ms, faster than 73.46% of Java online submissions for Search a 2D Matrix.Memory Usage: 38.8 MB, less than 0.96% of Java online submissions for Search a 2D Matrix.class Solution { public boolean searchMatrix(int[][] matrix, int target) { if (matrix.length == 0 || matrix[0].length == 0) { return false; } int m = matrix.length, n = matrix[0].length, row = 0; for (int i = 0; i < m; i++) { row = i; if (matrix[i][n - 1] >= target) { break; } } return Arrays.binarySearch(matrix[row], target) >= 0; }}