240. Search a 2D Matrix II

难度: Medium

题目描述

Write an efficient algorithm that searches for a value target in an m x n integer matrix matrix. This matrix has the following properties:

• Integers in each row are sorted in ascending from left to right.
• Integers in each column are sorted in ascending from top to bottom.

 

Example 1:

Input: 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]], target = 5
Output: true

Example 2:

Input: 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]], target = 20
Output: false

 

Constraints:

• m == matrix.length
• n == matrix[i].length
• 1 <= n, m <= 300
• -109 <= matrix[i][j] <= 109
• All the integers in each row are sorted in ascending order.
• All the integers in each column are sorted in ascending order.
• -109 <= target <= 109

解题思路

代码实现

解决方案

java

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

        int row = matrix.length;
        int col = matrix[0].length;
        int rowIndex = 0;
        int colIndex = col - 1;
        while (rowIndex < row && colIndex > -1) {
            if (matrix[rowIndex][colIndex] == target) {
                return true;
            } else if (matrix[rowIndex][colIndex] < target) {
                rowIndex++;
            } else {
                colIndex--;
            }
        }

        return false;

    }

}