LeetCode 74. Search a 2D Matrix（搜索矩阵）

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本文介绍了一种高效的算法，用于在一特殊性质的二维矩阵中查找特定值。该矩阵的每一行从左到右递增排序，并且每行的第一个元素大于前一行的最后一个元素。文章通过二分法实现了一个解决方案。

原题网址：https://leetcode.com/problems/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,   3,  5,  7],
  [10, 11, 16, 20],
  [23, 30, 34, 50]
]

Given target = 3, return true.

方法：二分法。

public class Solution {
    public boolean searchMatrix(int[][] matrix, int target) {
        if (matrix == null || matrix.length == 0 || matrix[0].length == 0) return false;
        int i=0, j=matrix.length * matrix[0].length - 1;
        while (i<=j) {
            int m = (i+j)/2;
            int row = m/matrix[0].length;
            int col = m%matrix[0].length;
            if (matrix[row][col] == target) return true;
            if (matrix[row][col] < target) i = m + 1; else j = m - 1;
        }
        return false;
    }
}