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GPS-Tracking-of-On-Campus-Walking-Project/MATLAB_Functions/HuskyTrack/gaimc/bfs.m
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function [d dt pred] = bfs(A,u,target) | |
% BFS Compute breadth first search distances, times, and tree for a graph | |
% | |
% [d dt pred] = bfs(A,u) returns the distance (d) and the discover time | |
% (dt) for each vertex in the graph in a breadth first search | |
% starting from vertex u. | |
% d = dt(i) = -1 if vertex i is not reachable from u | |
% pred is the predecessor array. pred(i) = 0 if vertex (i) | |
% is in a component not reachable from u and i != u. | |
% | |
% [...] = bfs(A,u,v) stops the bfs when it hits the vertex v | |
% | |
% Example: | |
% load_gaimc_graph('bfs_example.mat') % use the dfs example from Boost | |
% d = bfs(A,1) | |
% | |
% See also DFS | |
% David F. Gleich | |
% Copyright, Stanford University, 2008-20098 | |
% History | |
% 2008-04-13: Initial coding | |
if ~exist('target','var') || isempty(full), target=0; end | |
if isstruct(A), rp=A.rp; ci=A.ci; | |
else [rp ci]=sparse_to_csr(A); | |
end | |
n=length(rp)-1; | |
d=-1*ones(n,1); dt=-1*ones(n,1); pred=zeros(1,n); | |
sq=zeros(n,1); sqt=0; sqh=0; % search queue and search queue tail/head | |
% start bfs at u | |
sqt=sqt+1; sq(sqt)=u; | |
t=0; | |
d(u)=0; dt(u)=t; t=t+1; pred(u)=u; | |
while sqt-sqh>0 | |
sqh=sqh+1; v=sq(sqh); % pop v off the head of the queue | |
for ri=rp(v):rp(v+1)-1 | |
w=ci(ri); | |
if d(w)<0 | |
sqt=sqt+1; sq(sqt)=w; | |
d(w)=d(v)+1; dt(w)=t; t=t+1; pred(w)=v; | |
if w==target, return; end | |
end | |
end | |
end |