【LeetCode】Search a 2D Matrix (杨氏矩阵查找)

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.

  每一行递增，每一列递增，那么，从右上角（7）开始，如果该数小于target，那么往下走，如果该数大于target，那么往左走，知道查找到或者

  走出矩阵的范围。复杂度是O（m+n）

  import java.util.Arrays;public class Solution {    public boolean searchMatrix(int[][] matrix, int target) {        // Note: The Solution object is instantiated only once and is reused by each test case.        int m = matrix.length;        int n = matrix[0].length;        int i = 0, j = n - 1;        while(i < m && j >= 0)        {            if(matrix[i][j] == target)                return true;            else if(matrix[i][j] < target)                 i++;            else j--;        }        return false;    }}