mirror of
https://github.com/TheAlgorithms/Python.git
synced 2024-12-18 01:00:15 +00:00
122 lines
2.7 KiB
Python
122 lines
2.7 KiB
Python
from __future__ import print_function
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try:
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xrange #Python 2
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except NameError:
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xrange = range #Python 3
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'''
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Algorithm for calculating the most cost-efficient sequence for converting one string into another.
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The only allowed operations are
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---Copy character with cost cC
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---Replace character with cost cR
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---Delete character with cost cD
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---Insert character with cost cI
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'''
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def compute_transform_tables(X, Y, cC, cR, cD, cI):
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X = list(X)
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Y = list(Y)
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m = len(X)
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n = len(Y)
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costs = [[0 for _ in xrange(n+1)] for _ in xrange(m+1)]
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ops = [[0 for _ in xrange(n+1)] for _ in xrange(m+1)]
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for i in xrange(1, m+1):
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costs[i][0] = i*cD
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ops[i][0] = 'D%c' % X[i-1]
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for i in xrange(1, n+1):
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costs[0][i] = i*cI
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ops[0][i] = 'I%c' % Y[i-1]
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for i in xrange(1, m+1):
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for j in xrange(1, n+1):
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if X[i-1] == Y[j-1]:
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costs[i][j] = costs[i-1][j-1] + cC
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ops[i][j] = 'C%c' % X[i-1]
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else:
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costs[i][j] = costs[i-1][j-1] + cR
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ops[i][j] = 'R%c' % X[i-1] + str(Y[j-1])
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if costs[i-1][j] + cD < costs[i][j]:
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costs[i][j] = costs[i-1][j] + cD
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ops[i][j] = 'D%c' % X[i-1]
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if costs[i][j-1] + cI < costs[i][j]:
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costs[i][j] = costs[i][j-1] + cI
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ops[i][j] = 'I%c' % Y[j-1]
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return costs, ops
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def assemble_transformation(ops, i, j):
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if i == 0 and j == 0:
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seq = []
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return seq
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else:
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if ops[i][j][0] == 'C' or ops[i][j][0] == 'R':
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seq = assemble_transformation(ops, i-1, j-1)
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seq.append(ops[i][j])
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return seq
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elif ops[i][j][0] == 'D':
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seq = assemble_transformation(ops, i-1, j)
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seq.append(ops[i][j])
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return seq
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else:
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seq = assemble_transformation(ops, i, j-1)
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seq.append(ops[i][j])
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return seq
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if __name__ == '__main__':
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_, operations = compute_transform_tables('Python', 'Algorithms', -1, 1, 2, 2)
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m = len(operations)
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n = len(operations[0])
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sequence = assemble_transformation(operations, m-1, n-1)
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string = list('Python')
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i = 0
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cost = 0
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with open('min_cost.txt', 'w') as file:
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for op in sequence:
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print(''.join(string))
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if op[0] == 'C':
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file.write('%-16s' % 'Copy %c' % op[1])
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file.write('\t\t\t' + ''.join(string))
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file.write('\r\n')
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cost -= 1
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elif op[0] == 'R':
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string[i] = op[2]
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file.write('%-16s' % ('Replace %c' % op[1] + ' with ' + str(op[2])))
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file.write('\t\t' + ''.join(string))
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file.write('\r\n')
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cost += 1
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elif op[0] == 'D':
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string.pop(i)
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file.write('%-16s' % 'Delete %c' % op[1])
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file.write('\t\t\t' + ''.join(string))
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file.write('\r\n')
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cost += 2
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else:
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string.insert(i, op[1])
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file.write('%-16s' % 'Insert %c' % op[1])
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file.write('\t\t\t' + ''.join(string))
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file.write('\r\n')
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cost += 2
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i += 1
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print(''.join(string))
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print('Cost: ', cost)
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file.write('\r\nMinimum cost: ' + str(cost))
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