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@@ -0,0 +1,46 @@
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+#!/usr/bin/env python3
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+import sys
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+from operator import mul, floordiv, add, sub
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+
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+class Expr:
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+ def __init__(self, left, op, right):
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+ self.left = left
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+ self.op = op
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+ self.right = right
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+
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+ def __str__(self):
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+ return '(%s %s %s)' % (self.left, self.op, self.right)
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+
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+def simplify(expr, solve=None):
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+ if isinstance(expr, (int, str)):
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+ return expr
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+ left = simplify(expr.left)
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+ right = simplify(expr.right)
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+ if isinstance(left, int) and isinstance(right, int):
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+ fn = {'*': mul, '/': floordiv, '-': sub, '+': add}[expr.op]
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+ return fn(left, right)
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+ if isinstance(left, int) and expr.op in '*+':
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+ return simplify(Expr(right, expr.op, left))
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+ if expr.op == '=' and isinstance(left, Expr):
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+ if isinstance(left.right, int):
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+ inv = {'*': '/', '/': '*', '-': '+', '+': '-'}[left.op]
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+ return simplify(Expr(left.left, '=', Expr(right, inv, left.right)))
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+ if isinstance(left.left, int) and left.op == '-':
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+ return simplify(Expr(left.right, '=', Expr(left.left, '-', right)))
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+ if expr.op == '=' and left == solve:
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+ return right
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+ return Expr(left, expr.op, right)
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+
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+def parse(tasks, monkey):
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+ task = tasks[monkey]
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+ if ' ' in task:
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+ left, op, right = task.split()
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+ return Expr(parse(tasks, left), op, parse(tasks, right))
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+ return int(task) if task.isdigit() else task
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+
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+tasks = dict(line.rstrip().split(': ') for line in sys.stdin)
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+print(simplify(parse(tasks, 'root')))
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+tasks['humn'] = 'humn'
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+left, _, right = tasks['root'].split()
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+tasks['root'] = left + ' = ' + right
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+print(simplify(parse(tasks, 'root')))
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Taddeus Kroes