240. Search a 2D Matrix II

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.

要注意这道题目与Search a 2D Matrix的区别，这道题目每一行的第一个元素比上一行的第一个(与最后一个区分开来)元素大,

每次比较当前矩阵的右上角的元素与target的大小

class Solution {
public:
    bool searchMatrix(vector<vector<int>>& matrix, int target) {
        int row = 0;
        int col = matrix[0].size() - 1;

        while(row < matrix.size() && col >= 0){
            if(matrix[row][col] == target){
                return true;
            }else if(matrix[row][col] < target){
                row++;
            }else{
                col--;
            }
        }
        return false;
    }
};