Create an adjacency matrix based on graph information (MATLAB implementation)

Problem Description

The number of vertices in a weighted undirected graph is v, and the number of edges is e. When v is large, the number of elements in the adjacency matrix v*v is large, and manual creation is too troublesome.

Solution

step.1

According to all the edges in the graph (each edge contains two vertices i, j, and the weight w of the edge),

Create a text file tu.txt with a total of e lines and 3 columns,

The first column is i, the second column is j, the third column is w,

Each row contains information about an edge in the graph.

step.2

Write MATLAB functions,

Input: number of vertices, number of edges, matrix B with e rows and 3 columns (B is generated according to tu.txt)

Output: adjacency matrix G of the graph

function [G] = adjacentmatrix(v,e,B)
%   根据带权无向图的所有边组成的矩阵B，生成图的邻接矩阵G
G=inf(v);
for i=1:v
    for j=1:v
        if i==j
            G(i,j)=0;
        end
        for m=1:e
           if B(m,1)==i && B(m,2)==j 
               G(i,j)=B(m,3);
           elseif B(m,1)==j && B(m,2)==i
               G(i,j)=B(m,3);
           end
        end
    end
end

end

step.3

Execute the main function main

clear
clc
v=39;%顶点个数
e=54;%边数
%% 生成图的邻接矩阵G
fileID=fopen('tu.txt');%tu.txt文件每一行为（顶点1，顶点2，边的权值）
A=textscan(fileID,'%f %f %f');
fclose(fileID);
B=cell2mat(A);

G=adjacentmatrix(v,e,B);

Note: program structure

The following three files need to be placed in the same folder