I have file like this.
| From | To |
|---|---|
| 1 | 2 |
| 2 | 3 |
| 3 | 4 |
| 3 | 5 |
| 4 | 6 |
| 5 | 7 |
| 6 | 8 |
How can I find the path for each point?
For eg:
For 3 is [(1,2), (2,3)]
for 8 is [(1,2),(2,3),(3,4),(4,6),(6,8)]
Any Help would be appreciable!!!!!!!!!
2 Answers
A data structure like dict is more suitable to store the graph information.
Set To as index, so that given a node x we can find out prev node using df.loc[x, 'From']. Start from the destination node and keep moving to the previous node until you get 1(source node).
Use:
df = df.set_index('To')
x = 8
output = []
while x!=1:
y = df.loc[x, 'From']
output = [(y, x)] + output
x = y
Prints:
>>> output
[(1, 2), (2, 3), (3, 4), (4, 6), (6, 8)]
2 Comments
Abanish Tiwari
Thank you, I tried moving from forward to backward and that was must difficult since there can be multiple branches. I didn't think about the reverse that the last one would have only one point prior to it. It worked
Amit Vikram Singh
BFS is the most used algorithm for such purposes. However in your case, graph is a Tree which means there is a unique path from source to destination and we also have the access to back pointer from a node to its parent node, so here we can simply do backtracking(I hope it's correct name).
If it suits your purpose, you can resort to a "specialized" package for working with graphs. I'll give an example with networkx. In the example:
- I've taken the data you provided;
- converted it to
networkxGraph; - printed a list of the nodes (not the edges, note) that make your path;
- drawn a plot and saved it to a
.pngfile.
import networkx
import pandas as pd
import matplotlib.pyplot as plt
df = pd.DataFrame(data=[(1, 2), (2, 3), (3, 4), (3, 5), (4, 6), (6, 8)],
columns=['from', 'to'])
g = networkx.from_pandas_edgelist(df, source='from', target='to')
# Print a list of the nodes in the path from 1 to 8
print(networkx.shortest_path(g, source=1, target=8))
# Plot the graph
networkx.draw_networkx(g)
plt.savefig("test.png", format="PNG")
dict()and use bfs or dfs