搜索二维矩阵

Posted 2022-10-29 wakingshaw

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.

来源：力扣（LeetCode）
链接：https://leetcode-cn.com/problems/search-a-2d-matrix
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要求在一个二维矩阵找出目标数。借鉴其中一个题解的做法，从右上角开始遍历，目标数比右上角的数大，证明不在当前一行，行数+1；目标数比右上角的数小，证明不在当前一列，列数-1：

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