【LeetCode】74. Search a 2D Matrix

问题描述

https://leetcode.com/problems/search-a-2d-matrix/#/description

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.

算法

从左上角开始，一行一行地进行搜索，如果这一行的最后一个数小于target，那就移到下一行；否则，就在这一行搜索target

参考自：https://discuss.leetcode.com/topic/29159/java-clear-solution

算法

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