Split a String in Balanced Strings

A hand in blue light Photo by xandtor

This post is part of the Algorithms Problem Solving series.

Problem description

This is the Split a String in Balanced Strings problem. The description looks like this:

Balanced strings are those who have equal quantity of 'L' and 'R' characters.

Given a balanced string s split it in the maximum amount of balanced strings.

Return the maximum amount of splitted balanced strings.


Input: s = "RLRRLLRLRL"
Output: 4

Input: s = "RLLLLRRRLR"
Output: 3

Input: s = "LLLLRRRR"
Output: 1

Input: s = "RLRRRLLRLL"
Output: 2


The idea here is to iterate through the string and count each character. As we want to know the maximum number of balanced strings in the given string, we just need to compare the Ls and Rs as soon as possible. That way, when they are equal, it means that it is a balanced string, so we can sum in the max variable and reset the count again.

def balanced_string_split(s):
    els = 0
    ares = 0
    max = 0

    for char in s:
        if char == 'L':
            els += 1
            ares += 1

        if els == ares:
            max += 1
            els = 0
            ares = 0

    return max


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