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.

解题思路：

从右上角开始, 比较target 和 matrix[i][j]的值. 如果小于target, 则该行不可能有此数,  所以i++; 如果大于target, 则该列不可能有此数, 所以j--. 遇到边界则表明该矩阵不含target.

public class Solution {    public boolean searchMatrix(int[][] matrix, int target) {        int m = matrix.length;int n = matrix[0].length - 1;int i = 0;while (i < m && n >= 0) {<span style="white-space:pre"></span>if (target == matrix[i][n]) return true; else if (target > matrix[i][n]) {i++;}else {n--;}}return false;    }}