74. 搜索二维矩阵

bool searchMatrix(vector<vector<int>> &matrix, int target) {
    if(matrix.empty())
        return false;
    int l = 0, r = matrix.size() * matrix[0].size() - 1;

    while (l <= r) {
        int mid = l + ((r - l) >> 1);
        int row = mid / matrix[0].size(), col = mid % matrix[0].size();
        if (matrix[row][col] < target)
            l = mid + 1;
        else if (matrix[row][col] > target)
            r = mid - 1;
        else
            return true;
    }
    return false;
}