求任意兩點間最短距離及其路徑。(萬能最短路)
輸入:權值矩陣,起點,終點
輸出:最短距離矩陣,指定起訖點路徑(經過的頂點編號)
爲任意一點到其他點最短路奠定基礎
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function [P d]=liangdianzuiduanlu(W,qidian,zhongdian)
W;
n=length(W);
D=W;
m=1;
while m<=n
for i=1:n
for j=1:n
if D(i,j)>D(i,m)+D(m,j)
D(i,j)=D(i,m)+D(m,j);
end
end
end
m=m+1;
end
d=D(qidian,zhongdian);
P1=zeros(1,n);
k=1;
P1(k)=zhongdian;
V=ones(1,n)*inf;
kk=zhongdian;
while kk~=qidian;
for i=1:n
V(1,i)=D(qidian,kk)-W(i,kk);
if V(1,i)==D(qidian,i)
P1(k+1)=i;
kk=i;
k=k+1;
end
end
end
k=1;
wrow=find(P1~=0);
for j=length(wrow):(-1):1
P(k)=P1(wrow(j));
k=k+1;
end
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評:缺點是與人的銜接功能不好,下一篇《改進的任意兩點間最短距離及路
徑》將會解決這個缺點。
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例:求下圖中點1到8的最短距離和路徑
解:(1)寫權值矩陣
quanzhijuzhen=[ 0 2 8 1 Inf Inf Inf Inf
2 0 6 Inf 1 Inf Inf Inf
8 6 0 7 5 1 2 Inf
1 Inf 7 0 Inf Inf 9 Inf
Inf 1 5 Inf 0 3 Inf 8
Inf Inf 1 Inf 3 0 4 6
Inf Inf 2 9 Inf 4 0 3
Inf Inf Inf Inf 8 6 3 0]
(2)帶入程序
[P d]=liangdianzuiduanlu(quanzhijuzhen,1,8)
P =
1 2 5 8
d =
11
說明:路徑爲1->2->5->8,最短距離爲11.