[二分搜索] leetcode 74 Search a 2D Matrix

problem: https://leetcode.com/problems/search-a-2d-matrix/

        经典二分搜索。本质上还是一维数组。

class Solution {
public:
    bool searchMatrix(vector<vector<int>>& matrix, int target) {
        int m = matrix.size();
        if(!m) return false;
        int n = matrix[0].size();
        if(!n) return false;
        int low = 0;
        int high = m * n - 1;
        while(low <= high)
        {
            int mid = (low + high) / 2;
            int i = mid / n;
            int j = mid % n;
            if(matrix[i][j] == target)
            {
                return true;   
            }
            else if(matrix[i][j] > target)
            {
                high = mid - 1;
            }
            else 
            {
                low = mid + 1;
            }
        }
        return false;
    }
};