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* flake8 --max-line-length=88
* fixup! Format Python code with psf/black push
Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
120 lines
3.3 KiB
Python
120 lines
3.3 KiB
Python
"""
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Algorithm for calculating the most cost-efficient sequence for converting one string
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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 range(n + 1)] for _ in range(m + 1)]
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ops = [[0 for _ in range(n + 1)] for _ in range(m + 1)]
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for i in range(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 range(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 range(1, m + 1):
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for j in range(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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