search a 2D matrix

code

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

        int s = 0;
        int e = m*n-1;

        while(e > s+1)
        {
            int mid = (s+e)/2;
            int x = mid/n;
            int y = mid%n;
            if(matrix[x][y] == target)
            {
                return true;
            }
            else if(matrix[x][y] > target)
            {
                e = mid;
            }
            else
            {
                s = mid;
            }
        }

        int x = s/n;
        int y = s%n;

        if(matrix[x][y] == target)
        {
            return true;
        }

        x = e/n;
        y = e%n;

        if(matrix[x][y] == target)
        {
            return true;
        }

        return false;
    }
};