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zigzag.py
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zigzag.py
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# Zigzag scan of a matrix
# Argument is a two-dimensional matrix of any size,
# not strictly a square one.
# Function returns a 1-by-(m*n) array,
# where m and n are sizes of an input matrix,
# consisting of its items scanned by a zigzag method.
#
# Matlab Code:
# Alexey S. Sokolov a.k.a. nICKEL, Moscow, Russia
# June 2007
import numpy as np
def zigzag(input):
#initializing the variables
#----------------------------------
h = 0
v = 0
vmin = 0
hmin = 0
vmax = input.shape[0]
hmax = input.shape[1]
#print(vmax ,hmax )
i = 0
output = np.zeros(( vmax * hmax))
#----------------------------------
while ((v < vmax) and (h < hmax)):
if ((h + v) % 2) == 0: # going up
if (v == vmin):
#print(1)
output[i] = input[v, h] # if we got to the first line
if (h == hmax):
v = v + 1
else:
h = h + 1
i = i + 1
elif ((h == hmax -1 ) and (v < vmax)): # if we got to the last column
#print(2)
output[i] = input[v, h]
v = v + 1
i = i + 1
elif ((v > vmin) and (h < hmax -1 )): # all other cases
#print(3)
output[i] = input[v, h]
v = v - 1
h = h + 1
i = i + 1
else: # going down
if ((v == vmax -1) and (h <= hmax -1)): # if we got to the last line
#print(4)
output[i] = input[v, h]
h = h + 1
i = i + 1
elif (h == hmin): # if we got to the first column
#print(5)
output[i] = input[v, h]
if (v == vmax -1):
h = h + 1
else:
v = v + 1
i = i + 1
elif ((v < vmax -1) and (h > hmin)): # all other cases
#print(6)
output[i] = input[v, h]
v = v + 1
h = h - 1
i = i + 1
if ((v == vmax-1) and (h == hmax-1)): # bottom right element
#print(7)
output[i] = input[v, h]
break
#print ('v:',v,', h:',h,', i:',i)
return output
# Inverse zigzag scan of a matrix
# Arguments are: a 1-by-m*n array,
# where m & n are vertical & horizontal sizes of an output matrix.
# Function returns a two-dimensional matrix of defined sizes,
# consisting of input array items gathered by a zigzag method.
#
# Matlab Code:
# Alexey S. Sokolov a.k.a. nICKEL, Moscow, Russia
# June 2007
def inverse_zigzag(input, vmax, hmax):
#print input.shape
# initializing the variables
#----------------------------------
h = 0
v = 0
vmin = 0
hmin = 0
output = np.zeros((vmax, hmax))
i = 0
#----------------------------------
while ((v < vmax) and (h < hmax)):
#print ('v:',v,', h:',h,', i:',i)
if ((h + v) % 2) == 0: # going up
if (v == vmin):
#print(1)
output[v, h] = input[i] # if we got to the first line
if (h == hmax):
v = v + 1
else:
h = h + 1
i = i + 1
elif ((h == hmax -1 ) and (v < vmax)): # if we got to the last column
#print(2)
output[v, h] = input[i]
v = v + 1
i = i + 1
elif ((v > vmin) and (h < hmax -1 )): # all other cases
#print(3)
output[v, h] = input[i]
v = v - 1
h = h + 1
i = i + 1
else: # going down
if ((v == vmax -1) and (h <= hmax -1)): # if we got to the last line
#print(4)
output[v, h] = input[i]
h = h + 1
i = i + 1
elif (h == hmin): # if we got to the first column
#print(5)
output[v, h] = input[i]
if (v == vmax -1):
h = h + 1
else:
v = v + 1
i = i + 1
elif((v < vmax -1) and (h > hmin)): # all other cases
output[v, h] = input[i]
v = v + 1
h = h - 1
i = i + 1
if ((v == vmax-1) and (h == hmax-1)): # bottom right element
#print(7)
output[v, h] = input[i]
break
return output