File:PrimAlgDemo.gif
PrimAlgDemo.gif (314 × 323 pixels, file size: 248 KB, MIME type: image/gif, looped, 58 frames, 29 s)
File information
Structured data
Captions
Summary edit
DescriptionPrimAlgDemo.gif |
English: A demo for Prim's algorithm to find minimum spanning tree on a 2D plane. |
Date | |
Source | Own work |
Author | Shiyu Ji |
Python 3 Code edit
'''
Minimum Spanning Tree generation (SVG) for Prim's algorithm.
Firstly use this code to generate SVG frames.
Then transform to bitmaps and convert to GIF.
'''
# range size
N = 300
margin = 20
def norm(x, y):
return (x*x+y*y)**.5
def saveToSVG(nFrames, points, firmed, trying):
f = open('demo_'+'0'*(3-len(str(nFrames)))+str(nFrames)+'.svg', 'w')
f.write("<svg xmlns=\"http://www.w3.org/2000/svg\" version=\"1.1\">\n")
for p in points:
f.write("<circle cx=\"" +str(p[0]+margin)+ "\" cy=\""+ str(N-p[1]+margin) +"\" r=\"5\" fill=\"white\" stroke=\"black\"/>\n")
for L in firmed:
f.write("<line x1=\"" +str(L[0][0]+margin)+ "\" y1=\""+ str(N-L[0][1]+margin) +"\" x2=\"" + str(L[1][0]+margin) + "\" y2=\"" + str(N-L[1][1]+margin) + "\" stroke=\"red\" stroke-width=\"5\"/>\n")
for L in trying:
f.write("<line x1=\"" +str(L[0][0]+margin)+ "\" y1=\""+ str(N-L[0][1]+margin) +"\" x2=\"" + str(L[1][0]+margin) + "\" y2=\"" + str(N-L[1][1]+margin) + "\" stroke=\"blue\" stroke-width=\"5\"/>\n")
f.write("</svg>\n")
f.close()
def generatePoints(n):
import random as r
r.seed(100)
res = []
for i in range(n):
pt = [r.randint(0,N) for _ in [0, 1]]
if [pt] not in res:
res += [pt]
return res
def prim(n, points):
n = len(points)
mst = []
S = set()
import heapq
heap = []
nframe = 0
while len(mst)<n-1:
if len(S)==0:
topV = 0
else:
while heap[0][2] in S:
heapq.heappop(heap)
topV = heap[0][2]
saveToSVG(nframe, points, mst, [[points[heap[0][1]], points[heap[0][2]]]])
nframe+=1
mst.append([points[heap[0][1]], points[topV]])
heapq.heappop(heap)
saveToSVG(nframe, points, mst, [])
nframe+=1
S.add(topV)
for i in range(n):
if i not in S:
L = norm(points[i][0]-points[topV][0], points[i][1]-points[topV][1])
heapq.heappush(heap, [L, topV, i])
return mst
# test 30 points temporarily
n = 30
pts = generatePoints(n)
prim(n, pts)
Licensing edit
I, the copyright holder of this work, hereby publish it under the following license:
This file is licensed under the Creative Commons Attribution-Share Alike 4.0 International license.
- You are free:
- to share – to copy, distribute and transmit the work
- to remix – to adapt the work
- Under the following conditions:
- attribution – You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
- share alike – If you remix, transform, or build upon the material, you must distribute your contributions under the same or compatible license as the original.
File history
Click on a date/time to view the file as it appeared at that time.
Date/Time | Thumbnail | Dimensions | User | Comment | |
---|---|---|---|---|---|
current | 12:52, 24 December 2016 | 314 × 323 (248 KB) | Shiyu Ji (talk | contribs) | User created page with UploadWizard |
You cannot overwrite this file.
File usage on Commons
The following page uses this file:
File usage on other wikis
The following other wikis use this file:
- Usage on ar.wikipedia.org
- Usage on en.wikipedia.org
- Usage on hu.wikipedia.org
- Usage on it.wikipedia.org
- Usage on ka.wikipedia.org
- Usage on sr.wikipedia.org
- Usage on zh-min-nan.wikipedia.org