LeetCode120|二维数组中的查找

现有矩阵 matrix 如下：

[
  [1,   4,  7, 11, 15],
  [2,   5,  8, 12, 19],
  [3,   6,  9, 16, 22],
  [10, 13, 14, 17, 24],
  [18, 21, 23, 26, 30]
]
给定 target = 5，返回 true。

给定 target = 20，返回 false。

 

限制：

0 <= n <= 1000

0 <= m <= 1000
 

import java.util.HashSet;

public class FindNumberIn2DArrayTest {
    public static void main(String[] args) {
        int[][] matrix = {
                {1, 4, 7, 11, 15},
                {2, 5, 8, 12, 19},
                {3, 6, 9, 16, 22},
                {10, 13, 14, 17, 24},
                {18, 21, 23, 26, 30}
        };
        int target = 5;
        boolean numberIn2DArray = findNumberIn2DArray(matrix, target);
        System.out.println("numberIn2DArray = " + numberIn2DArray);

    }

    public static boolean findNumberIn2DArray(int[][] matrix, int target) {
        if (matrix == null || matrix.length == 0 || matrix[0].length == 0) {
            return false;
        }
        int rowLength = matrix.length;
        int colLength = matrix[0].length - 1;
        int row = 0;
        while (row < rowLength && colLength >= 0) {
            if (matrix[row][colLength] == target) {
                return true;
            } else if (matrix[row][colLength] > target) {
                colLength--;
            } else {
                row++;
            }
        }
        return false;
    }

    public static boolean findNumberIn2DArray2(int[][] matrix, int target) {
        if (matrix == null || matrix.length == 0 || matrix[0].length == 0) {
            return false;
        }
        HashSet<Integer> hashSet = new HashSet<>(matrix.length * matrix[0].length);
        int rowLength = matrix.length;
        int colLength = matrix[0].length;
        for (int i = 0; i < rowLength; i++) {
            for (int j = 0; j < colLength; j++) {
                if (hashSet.contains(target)) {
                    return true;
                }
                hashSet.add(matrix[i][j]);
            }
        }
        return hashSet.contains(target);
    }
}