Created
May 16, 2017 02:03
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inputs = [ | |
'1 + 1', | |
'2 * 2', | |
'1 + 2 * 3', | |
'( 1 + 2 ) * 3' | |
] | |
def pemdas(s): | |
ops = { op: p for p, l in enumerate(['+-', '*/']) for op in l } | |
ostk = [] | |
out = [] | |
for tok in s.split(' '): | |
if tok.isdigit(): | |
out.append(tok) | |
elif tok in ops: | |
while ostk and ostk[-1] not in '()' and ops[tok] <= ops[ostk[-1]]: | |
out.append(ostk.pop()) | |
ostk.append(tok) | |
elif tok == '(': | |
ostk.append(tok) | |
elif tok == ')': | |
while ostk[-1] != '(': | |
out.append(ostk.pop()) | |
ostk.pop() | |
while ostk: | |
out.append(ostk.pop()) | |
stk = [] | |
for v in out: | |
if v.isdigit(): | |
stk.append(int(v)) | |
elif v in ops: | |
stk.append({ | |
'+': lambda x, y: x + y, | |
'-': lambda x, y: x - y, | |
'*': lambda x, y: x * y, | |
'/': lambda x, y: x / y, | |
}[v](stk.pop(), stk.pop())) | |
return stk[0] | |
print '\n'.join(str(pemdas(i)) for i in inputs) |
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