Szathmáry László honlapja @ DEIK

Parentheses

Consider an expression that contains numbers, parentheses, and operators. Now we are only interested in the parentheses. Three kind of parentheses can be present: "{}", "()", "[]". If a parenthesis is opened, then it must be closed with its pair (of the same type). The scope of the parentheses cannot cross each other. Exercise: having an expression, decide if its parentheses are correct (don't bother about the numbers and operators this time).

Examples:

test("((5+3)*2+1)") == True
test("{[(3+1)+2]+}") == True
test("(3+{1-1)}") == False
test("[1+1]+(2*2)-{3/3}") == True
test("(({[(((1)-2)+3)-3]/3}-3)") == False

Tip: what data structure should we use?

20130902e