I get as an input N*M matrix (tuple of tuples), values from 1 to 9.
What is the best way to hash this structure, so I can get the place (x,y) of every 8 value? (8 for example, can be 5 or 7...)
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3 Answers
Since you want to find the location of 5s and 7s and 8s, it may be more efficient to store all the locations in a dict with one pass through the matrix, instead of one pass for the 5s, one pass for the 7s, etc...
loc = {}
for x in range(N):
for y in range(M):
loc.setdefault(matrix[x][y], []).append((x,y))
2 Comments
Onca
but I would like to access with O(1), since my program searches all the time for values in changing matrix
unutbu
Dict access is O(1). See the TimeComplexity wiki.
"Hash" is the wrong word for this. You just want to search a 2D array for a particular value. Maybe something like this...
height = len(data)
width = len(data[0])
eights = [(x, y) for y in range(height) for x in range(width) if data[x][y] == 8]
1 Comment
Onca
but I would like to access with O(1), since my program searches all the time for values in changing matrix
[(x,y) for x in range(N) for y in range(M) if matrix[x][y] == 8]
