LeetCode -- Search a 2D Matrix II

LeetCode -- Search a 2D Matrix II

題目描述：
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.


本題看起來是Search a 2D Matrix的擴展問題，其實和第一題的思路完全不一樣。比較精簡的思路是：
1.從左下開始找，如果matrix[r,c]（r為行，c為列） < target，c++；否則r--。
2.直到r或c越界為止。




實現代碼：

public class Solution {
    public bool SearchMatrix(int[,] matrix, int target) 
    {
        var rowLen = matrix.GetLength(0);
        var colLen = matrix.GetLength(1);
        
        var row = rowLen - 1;
        var col = 0;
        
        while(col <= colLen - 1 && row >= 0){
            if(matrix[row,col] == target){
                return true;
            }
            else if(matrix[row,col] < target){
                col ++;
            }
            else{
                row --;
            }
        }
        return false;
    }


}