hot100_74. 搜索二维矩阵

给你一个满足下述两条属性的 m x n 整数矩阵：
每行中的整数从左到右按非严格递增顺序排列。
每行的第一个整数大于前一行的最后一个整数。
给你一个整数 target ，如果 target 在矩阵中，返回 true ；否则，返回 false 。

示例 1：

输入：matrix = [[1,3,5,7],[10,11,16,20],[23,30,34,60]], target = 3
输出：true

示例 2：

输入：matrix = [[1,3,5,7],[10,11,16,20],[23,30,34,60]], target = 13
输出：false

思路

class Solution {public boolean searchMatrix(int[][] matrix, int target) {int rowindex = binarySearchFirstColumn(matrix, target);if (rowindex < 0) {return false;}return binarySearchRow(matrix[rowindex], target);}public int binarySearchFirstColumn(int[][] matrix, int target) {int low = -1, high = matrix.length - 1;while (low < high) {int mid = (high - low + 1) / 2 + low;if (matrix[mid][0] <= target) {low = mid;} else {high = mid - 1;}}return low;}public boolean binarySearchRow(int[] row, int target) {int low = 0, high = row.length - 1;while (low <= high) {int mid = (high - low) / 2 + low;if (row[mid] == target) {return true;} else if (row[mid] > target) {high = mid - 1;} else {low = mid + 1;}}return false;}}