LeetCode——Search a 2D Matrix

標籤：leetcode   二分尋找   

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,   3,  5,  7],  [10, 11, 16, 20],  [23, 30, 34, 50]]

Given target = 3, return true.

原題連結：https://oj.leetcode.com/problems/search-a-2d-matrix/

題目：在m * n 的矩陣中尋找目標值是否存在。

比較好的辦法就是二分尋找，即將矩陣整體看成一個數組來處理。

public boolean searchMatrix(int[][] matrix, int target) {if(matrix == null || matrix.length == 0 || matrix[0].length == 0)return false;int m = matrix.length;int n = matrix[0].length;int start = 0;int end = m * n - 1;while (start <= end) {int mid = (start + end) / 2;int x = mid / n;int y = mid % n;if (matrix[x][y] == target)return true;if (matrix[x][y] < target)start = mid + 1;elseend = mid - 1;}return false;}

LeetCode——Search a 2D Matrix