LeetCode/src/main/java/L0074_SearchA2DMatrix.java at master · LjyYano/LeetCode · GitHub

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/**

* https://leetcode.cn/problems/search-a-2d-matrix/

* 编写一个高效的算法来判断 m x n 矩阵中，是否存在一个目标值。该矩阵具有如下特性：

* - 每行中的整数从左到右按升序排列。

* - 每行的第一个整数大于前一行的最后一个整数。

* 示例 1：

* 输入：matrix = [[1,3,5,7],[10,11,16,20],[23,30,34,60]], target = 3

* 输出：true

* 示例 2：

* 输入：matrix = [[1,3,5,7],[10,11,16,20],[23,30,34,60]], target = 13

* 输出：false

* 提示：

* m == matrix.length

* n == matrix[i].length

* 1 <= m, n <= 100

* -10⁴ <= matrix[i][j], target <= 10⁴

public class L0074_SearchA2DMatrix {

public boolean searchMatrix(int[][] matrix, int target) {

if (matrix == null || matrix.length == 0 || matrix[0].length == 0) {

return false;

}

int m = matrix.length;

int n = matrix[0].length;

// 将二维矩阵转换为一维数组进行二分查找

int left = 0;

int right = m * n - 1;

while (left <= right) {

int mid = left + (right - left) / 2;

// 将一维索引转换为二维坐标

int row = mid / n;

int col = mid % n;

int value = matrix[row][col];

if (value == target) {

return true;

} else if (value < target) {

left = mid + 1;

} else {

right = mid - 1;

}

return false;

}

public static void main(String[] args) {

L0074_SearchA2DMatrix solution = new L0074_SearchA2DMatrix();

// 测试用例 1

int[][] matrix1 = {

{1, 3, 5, 7},

{10, 11, 16, 20},

{23, 30, 34, 60}

};

int target1 = 3;

System.out.println("测试用例 1：");

System.out.println("目标值 " + target1 + " 是否存在：" + solution.searchMatrix(matrix1, target1)); // 预期输出：true

// 测试用例 2

int[][] matrix2 = {

{1, 3, 5, 7},

{10, 11, 16, 20},

{23, 30, 34, 60}

};

int target2 = 13;

System.out.println("\n测试用例 2：");

System.out.println("目标值 " + target2 + " 是否存在：" + solution.searchMatrix(matrix2, target2)); // 预期输出：false

}

LeetCode/src/main/java/L0074_SearchA2DMatrix.java at master · LjyYano/LeetCode · GitHub

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