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Why doesn't Dijkstra's algorithm work for negative weight edges?
...e true. For example:
A
/ \
/ \
/ \
5 2
/ \
B--(-10)-->C
V={A,B,C} ; E = {(A,C,2), (A,B,5), (B,C,-10)}
Dijkstra from A will first develop C, and will later fail to find A->B->C
EDIT a bit deeper explanation:
Note that this is important...
What programming practice that you once liked have you since changed your mind about? [closed]
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votes
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Automatically start forever (node) on system restart
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edited Nov 9 '15 at 17:28
cedricbellet
14811 silver badge1212 bronze badges
answered Nov 14 '12 at 22...
Ignore outliers in ggplot2 boxplot
How would I ignore outliers in ggplot2 boxplot? I don't simply want them to disappear (i.e. outlier.size=0), but I want them to be ignored such that the y axis scales to show 1st/3rd percentile. My outliers are causing the "box" to shrink so small its practically a line. Are there some techniques...
ERROR:'keytool' is not recognized as an internal or external command, operable program or batch file
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26 Answers
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Writing Unicode text to a text file?
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323
Deal exclusively with unicode objects as much as possible by decoding things to unicode objects...
What is the preferred syntax for initializing a dict: curly brace literals {} or the dict() function
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243
Curly braces. Passing keyword arguments into dict(), though it works beautifully in a lot of s...
MySQL Conditional Insert
...sert, try:
INSERT INTO x_table(instance, user, item)
SELECT 919191, 123, 456
FROM dual
WHERE NOT EXISTS (SELECT * FROM x_table
WHERE user = 123
AND item = 456)
In this, dual is a table with one row only (found origi...
How do I convert a numpy array to (and display) an image?
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240
You could use PIL to create (and display) an image:
from PIL import Image
import numpy as np
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Find integer index of rows with NaN in pandas dataframe
...an use to index back into df, e.g.:
df['a'].ix[index[0]]
>>> 1.452354
For the integer index:
df_index = df.index.values.tolist()
[df_index.index(i) for i in index]
>>> [3, 6]
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