function adjacencyMatrix = calculateDistanceMatrix(positions)
    % 计算任意两个城市之间的直线距离，返回加权邻接矩阵
    % 输入：positions - 包含城市坐标的矩阵 (n行3列)
    % 输出：adjacencyMatrix - n×n的加权邻接矩阵
    
    % 获取城市数量
    numCities = size(positions, 1);
    
    % 初始化邻接矩阵
    adjacencyMatrix = zeros(numCities, numCities);
    
    % 计算每对城市之间的欧几里得距离
    for i = 1:numCities
        for j = 1:numCities
            if i ~= j
                % 计算欧几里得距离
                dx = positions(i, 2) - positions(j, 2);
                dy = positions(i, 3) - positions(j, 3);
                adjacencyMatrix(i, j) = sqrt(dx^2 + dy^2);
            end
        end
    end
end