240. Search a 2D Matrix II

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本文介绍了一种高效的矩阵搜索算法，该算法能在按行和列都升序排列的矩阵中查找特定值。通过实例演示了如何逐步缩小搜索范围直至找到目标值或确定目标值不存在于矩阵中。

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

For example,

Consider the following 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]
]

Given target = 5, return true.

Given target = 20, return false.

class Solution {
public:
    bool searchMatrix(vector<vector<int>>& matrix, int target) {
        
        bool found = false;
        if(matrix.size()==0) return found;
        
        int rows = matrix.size();
        int columns = matrix[0].size();
        int row = 0;
        int column = columns - 1;
        while(row<rows&&column>=0)
        {
            if(matrix[row][column]==target)
            {
                found = true;
                break;
            }else if(matrix[row][column]>target)
            {
                --column;
            }else
                ++row;
        }
        
        return found;
        
    }
};