Problem 111. Find matching parenthesis

Created by Aleksey

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One of the most indispensable things about a great text editor for programming is the ability to quickly jump between matching parentheses. If you have a line like,
    if (f(a) >= b(c, d(e*(f-g))))
it very convenient to place your cursor at, say, the second to last closing parenthesis, and have the editor show you where is the matching opening parenthesis. (In this example, it is the one just after b.)
For this problem, you should write a function that takes a string s like 'if (f(a) >= b(c, d(e*f(-g))))' and an integer n representing a character position within the string. Your function should return the index of the matching parenthesis.
For example:
    >> s = 'if (f(a) >= b(c, d(e*f(-g))))';
    >> find_matching_paren(s, 4)
    ans =
        29
    >> find_matching_paren(s, 6)
    ans =
         8
    >> find_matching_paren(s, 27)
    ans =
        19
You can assume that n will always be the position of either an open or closing parenthesis.
You can assume the string will always have balanced parentheses.

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Last Solution submitted on Jan 14, 2026

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3 Comments

Qianqian Fang on 6 May 2019

wondering if there is a place I can review the submitted solution source codes? I think this is a great place to learn about matlab programming.

goc3 on 17 May 2019

@Qianqian Fang: once you've solved a problem, click on the solution map (containing all the green circles and orange x's). On that separate page you can click on each of the shapes to view each solution below the chart.

Nikolaos Nikolaou on 30 Jul 2019

somehow i get that s='()' is there something wrong with the test suite?

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