leetcode--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.

题意：给定一个矩阵。对于每一行，从左到右递增，对应每一列，从上到下递增。求指定target是否在矩阵中

分类：数组，二分法

解法1：target和右上角的元素比较，如果比它大说明在下一行，如果比它小，说明在它的列之前

这样就可以快速划分行列范围

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