用MATLAB编写蚁群算法求解TSP问题的代码

以下是用MATLAB编写蚁群算法求解TSP问题的基本代码：

% 定义TSP问题的城市数量
n = 20;

% 生成城市坐标
x = rand(n,1);
y = rand(n,1);

% 计算城市间距离
dist = zeros(n,n);
for i = 1:n
    for j = i:n
        dist(i,j) = sqrt((x(i)-x(j))^2 + (y(i)-y(j))^2);
        dist(j,i) = dist(i,j);
    end
end

% 设置蚂蚁数量和迭代次数
m = 50;
num_iter = 200;

% 初始化信息素矩阵
pheromone = ones(n,n);

% 初始化最优解和最优距离
best_sol = zeros(num_iter,n);
best_dist = Inf;

% 开始迭代
for iter = 1:num_iter
    % 初始化蚂蚁位置和已访问城市集合
    pos = zeros(m,1);
    visited = zeros(m,n);
    
    % 计算蚂蚁路径
    for i = 1:m
        % 选择下一个城市
        while length(find(visited(i,:)==0)) > 0
            current = pos(i);
            unvisited = find(visited(i,:)==0);
            prob = pheromone(current,unvisited);
            prob = prob / sum(prob);
            next = randsample(unvisited,1,true,prob);
            visited(i,next) = 1;
            pos(i) = next;
        end
    end
    
    % 计算每个蚂蚁的路径长度
    dists = zeros(m,1);
    for i = 1:m
        path = [pos(i:end); pos(1:i-1)];
        for j = 1:n-1
            dists(i) = dists(i) + dist(path(j),path(j+1));
        end
        dists(i) = dists(i) + dist(path(n),path(1));
    end
    
    % 更新最优解和最优距离
    [min_dist,idx] = min(dists);
    if min_dist < best_dist
        best_dist = min_dist;
        best_sol(iter,:) = [pos(idx:end); pos(1:idx-1)];
    else
        best_sol(iter,:) = best_sol(iter-1,:);
    end
    
    % 更新信息素矩阵
    delta_pheromone = zeros(n,n);
    for i = 1:m
        path = [pos(i:end); pos(1:i-1)];
        for j = 1:n-1
            delta_pheromone(path(j),path(j+1)) = delta_pheromone(path(j),path(j+1)) + 1/dists(i);
            delta_pheromone(path(j+1),path(j)) = delta_pheromone(path(j),path(j+1));
        end
        delta_pheromone(path(n),path(1)) = delta_pheromone(path(n),path(1)) + 1/dists(i);
        delta_pheromone(path(1),path(n)) = delta_pheromone(path(n),path(1));
    end
    pheromone = (1-0.1)*pheromone + delta_pheromone;
end

% 输出最优解和最优距离
disp('Best solution:');
disp(best_sol(end,:));
disp('Best distance:');
disp(best_dist);

此代码实现了基本的蚁群算法框架，包括城市坐标生成、城市间距离计算、蚂蚁路径选择、信息素更新等步骤。你可以根据自己的需要进行修改和扩展。