leetcode74. Search a 2D Matrix
来源:互联网 发布:y系列电机铁芯数据大全 编辑:程序博客网 时间:2024/05/29 08:18
74. 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.
解法一
两次二分查找,先查找target所在哪个一维数组中,然后在该一维数组中进行二分查找。
public class Solution { public boolean searchMatrix(int[][] matrix, int target) { // 异常处理,如果二维数组长度=0或为null或者为{{}},返回false if(matrix.length == 0 || matrix == null || matrix[matrix.length - 1].length == 0) { return false; } int index = 0; int start = 0; int end = matrix.length - 1; int mid; // 如果数组的最后一个数小于target,或者第一个数大于target,返回false if(matrix[end][matrix[0].length - 1] < target || matrix[start][0] > target) { return false; } while (start < end - 1) { mid = start + (end - start) / 2; if (matrix[mid][0] == target) { return true; } else if (matrix[mid][0] < target) { start = mid; } else { end = mid; } } // 判断第一个大于target的位置,则target所在的位置为该位置前的一个数组中, if (matrix[start][0] == target) { return true; } else if (matrix[end][0] == target) { return true; } else if(matrix[start][0] > target) { index = start - 1; } else if(matrix[end][0] > target) { index = end - 1; // 如果最后一个数组的第一个值仍比target小,则target所在的位置为最后一个数组 } else { index = end; } // 找到target所在的数组,对该数组进行二分查找 start = 0; end = matrix[index].length - 1; while (start < end - 1) { mid = start + (end - start) / 2; if (matrix[index][mid] == target) { return true; } if (matrix[index][mid] < target) { start = mid; } if (matrix[index][mid] > target) { end = mid; } } if (matrix[index][start] == target) { return true; } else if (matrix[index][end] == target) { return true; } else { return false; } }}
解法二
一次二分查找,通过number = matrix[mid / column][mid % column]对应每一个数值。
public class Solution { public boolean searchMatrix(int[][] matrix, int target) { // 异常处理,如果二维数组长度=0或为null返回false if(matrix.length == 0 || matrix == null) { return false; } // 如果{{}},返回false if (matrix[0].length == 0 || matrix[0] == null) { return false; } int row = matrix.length; int column = matrix[0].length; int start = 0; int end = row * column - 1; int mid, number; // 如果数组的最后一个数小于target,或者第一个数大于target,返回false。提升性能 if(matrix[row - 1][column - 1] < target || matrix[0][0] > target) { return false; } while (start + 1 < end) { mid = start + (end - start) / 2; number = matrix[mid / column][mid % column]; if (number == target) { return true; } else if (number < target) { start = mid; } else { end = mid; } } if (matrix[start / column][start % column] == target) { return true; } else if (matrix[end / column][end % column] == target) { return true; } return false; }}
0 0
- [LeetCode74]Search a 2D Matrix
- [LeetCode74]Search a 2D Matrix
- Leetcode74. Search a 2D Matrix
- leetcode74. Search a 2D Matrix
- LeetCode74 Search a 2D Matrix
- LeetCode74——Search a 2D Matrix
- Search a 2D Matrix
- Search a 2D Matrix
- Search a 2D Matrix
- Search a 2D Matrix
- Search a 2D Matrix
- Search a 2D Matrix
- Search a 2D Matrix
- Search a 2D Matrix
- Search a 2D Matrix
- Search a 2D Matrix
- Search a 2D Matrix
- Search a 2D Matrix
- android 定位服务
- 使用 Redis Bitmap 实现用户上线次数统计
- 【b404】虫食算
- 论学习的重要性之 -- 影院售票系统
- 使用锚文本链接导航,让你的网站生动起来
- leetcode74. Search a 2D Matrix
- 使用RocketMQ的客户端使用
- swift初探:一些简单的实用性方法和一个上下滑动拉伸图片的简单动画
- js对象构造方法
- 前端开发面试题之 JavaScript
- log4j.properties 详解与配置步骤
- 264. Ugly Number II
- ThinkPHP框架简单应用之mysql增删改查
- listener.ora 、sqlnet.ora 、tnsnames.ora