matlab 实现堆优化的迪杰斯特拉算法

迪杰斯特拉算法详细算法我就不多比比啦,本人比较懒。我看了下网上好像没有matlab 版堆优化的迪杰斯特拉,索性自己写了一个。

堆也是自己写的,详情参见我的另一篇文章 https://blog.csdn.net/shengsikandan/article/details/105396751

代码涉及到技术包括:使用元胞数组作为结构的最小堆,使用元胞数组实现类似c++里的vector容器

D = [ [0,12,inf,inf,inf,16,14],       %距离矩阵
        [12,0,10,inf,inf,7,inf],
        [inf,10,0,3,5,6,inf],
        [inf,inf,3,0,4,inf,inf],
        [inf,inf,5,4,0,2,8],
        [16,7,6,inf,2,0,9],
        [14,inf,inf,inf,8,9,0]
      ];
n = 7;

% --------------------------------------------------------------
% 构造node节点容器,是一个元胞数组矩阵,元素有两个值。
% 第一个值是节点编号,第二个值是该点与点i(矩阵第i行)的距离
node = {};
for i = 1:n
    k = 1;
    for j = 1:n
        if D(i,j) < inf && D(i,j) ~=0
            node{i,k} = {j;D(i,j)};
            k = k + 1;
        end
    end
end
% --------------------------------------------------------------

dis = ones(n)*inf;   % 最终的最短路径矩阵;

% --------------------------------------------------------------
% 迪杰斯特拉算法核心部分  该部分求的是任意两点的最短距离
%s = 6;
for s = 1:n
    dis(s,s) = 0;
    hp = make_heap({});           %建立一个空堆
    hp = push(hp,s,0);       
    while ~isempty(hp)
        tmpid = cell2mat(hp{1}(1));
        tmpd = cell2mat(hp{1}(2));
        hp = pop(hp);
        i = 1;
        n = length({node{tmpid,:}});
        while i <= n && ~isempty(cell2mat(node{tmpid,i}))
            pos = cell2mat(node{tmpid,i}(1));
            ds = tmpd + cell2mat(node{tmpid,i}(2));
            if dis(s,pos) > ds
                dis(s,pos) = ds;
                hp = push(hp,pos,ds);
            end
            i = i + 1;
        end
    end  
end
% --------------------------------------------------------------
dis

function a = swap(a,i,j)  %交换数组的两个元素 
    t = a{i};
    a{i} = a{j};
    a{j} = t;
end

% 向下调整函数
function a = shiftdown(a,i)
    n = length(a);
    if 2*i <= n && 2*i+1 <= n && i <= n
        if cell2mat(a{i}(2)) > cell2mat(a{2*i}(2))
            a = swap(a,i,2*i);
            a = shiftdown(a,2*i);
        end
        if cell2mat(a{i}(2)) > cell2mat(a{2*i+1}(2))
            a = swap(a,i,2*i+1);
            a = shiftdown(a,2*i+1);
        end
    elseif 2*i <= n
        if cell2mat(a{i}(2)) > cell2mat(a{2*i}(2))
            a = swap(a,i,2*i);
            a = shiftdown(a,2*i);
        end
    end
end
% 构造一个最小堆
function a = make_heap(a)   
    n = length(a);
    for i = n/2:-1:1
        a = shiftdown(a,i);
    end
end

% 弹出堆顶元素
function a = pop(a)
    a(1) = [];
    n = length(a);
    a = shiftdown(a,1);
end

%添加一个元素
function a = push(a,id,value)
    n = length(a)+1;
    a{n} = {id;value};
    n = length(a);
    while n>=2
        parent = floor(n/2);
        if cell2mat(a{n}(2)) < cell2mat(a{parent}(2))
            a = swap(a,parent,n);
        end
        n = parent;
    end
end

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转载自blog.csdn.net/shengsikandan/article/details/105460115