以上代码还是不完整，请用matlab编写完整的用蚁群算法解决多旅行商问题的代码

以下是使用蚁群算法解决多旅行商问题的完整 MATLAB 代码。其中，我们使用了蚁群算法中的基本公式来更新信息素和蚂蚁的选择概率，并使用迭代优化来不断寻找最优解。

% 定义问题参数
num_cities = 10;    % 城市数量
num_ants = 20;      % 蚂蚁数量
num_iterations = 100;   % 迭代次数
Q = 100;            % 信息素增加强度
rho = 0.1;          % 信息素挥发强度
alpha = 1;          % 信息素重要程度
beta = 5;           % 启发函数重要程度
tau0 = 10 * (1 / num_cities);   % 初始信息素强度
distance_matrix = rand(num_cities);   % 城市间距离矩阵

% 初始化信息素和蚂蚁位置
tau = tau0 * ones(num_cities, num_cities);
best_tour_length = Inf;
best_tour = [];

for i = 1:num_iterations
    % 初始化蚂蚁位置和已访问城市
    ant_tours = zeros(num_ants, num_cities);
    ant_tours_lengths = Inf(num_ants, 1);
    unvisited_cities = 1:num_cities;
    
    % 让每只蚂蚁进行巡逻
    for j = 1:num_ants
        current_city = randi(num_cities);
        ant_tours(j, 1) = current_city;
        unvisited_cities(current_city) = [];
        
        for k = 2:num_cities
            % 计算当前城市和未访问城市之间的信息素和启发值
            p = tau(current_city, unvisited_cities).^alpha .* (1 ./ distance_matrix(current_city, unvisited_cities)).^beta;
            p = p / sum(p);
            
            % 用轮盘赌选择下一个城市
            cum_prob = cumsum(p);
            r = rand();
            next_city_idx = find(cum_prob >= r, 1);
            next_city = unvisited_cities(next_city_idx);
            
            % 更新蚂蚁位置和已访问城市
            ant_tours(j, k) = next_city;
            unvisited_cities(next_city_idx) = [];
            current_city = next_city;
        end
        
        % 计算蚂蚁路径长度
        tour_length = 0;
        for k = 1:num_cities-1
            tour_length = tour_length + distance_matrix(ant_tours(j,k), ant_tours(j,k+1));
        end
        tour_length = tour_length + distance_matrix(ant_tours(j,num_cities), ant_tours(j,1));
        ant_tours_lengths(j) = tour_length;
        
        % 更新最优路径
        if tour_length < best_tour_length
            best_tour_length = tour_length;
            best_tour = ant_tours(j, :);
        end
    end
    
    % 更新信息素
    delta_tau = zeros(num_cities, num_cities);
    for j = 1:num_ants