# 1221. Split a String in Balanced Strings

## Description

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

Given a balanced string s, split it into some number of substrings such that:

• Each substring is balanced.

Return the maximum number of balanced strings you can obtain.

Example 1:

Input: s = "RLRRLLRLRL"
Output: 4
Explanation: s can be split into "RL", "RRLL", "RL", "RL", each substring contains same number of 'L' and 'R'.


Example 2:

Input: s = "RLRRRLLRLL"
Output: 2
Explanation: s can be split into "RL", "RRRLLRLL", each substring contains same number of 'L' and 'R'.
Note that s cannot be split into "RL", "RR", "RL", "LR", "LL", because the 2nd and 5th substrings are not balanced.

Example 3:

Input: s = "LLLLRRRR"
Output: 1
Explanation: s can be split into "LLLLRRRR".


Constraints:

• 2 <= s.length <= 1000
• s[i] is either 'L' or 'R'.
• s is a balanced string.

## Solutions

Solution 1: Greedy

We use a variable $l$ to maintain the current balance of the string, i.e., the value of $l$ is the number of ‘L’s minus the number of ‘R’s in the current string. When the value of $l$ is 0, we have found a balanced string.

We traverse the string $s$. When we traverse to the $i$-th character, if $s[i] = L$, then the value of $l$ is increased by 1, otherwise, the value of $l$ is decreased by 1. When the value of $l$ is 0, we increase the answer by 1.

The time complexity is $O(n)$, and the space complexity is $O(1)$. Here, $n$ is the length of the string $s$.

• class Solution {
public int balancedStringSplit(String s) {
int ans = 0, l = 0;
for (char c : s.toCharArray()) {
if (c == 'L') {
++l;
} else {
--l;
}
if (l == 0) {
++ans;
}
}
return ans;
}
}

• class Solution {
public:
int balancedStringSplit(string s) {
int ans = 0, l = 0;
for (char c : s) {
if (c == 'L')
++l;
else
--l;
if (l == 0) ++ans;
}
return ans;
}
};

• class Solution:
def balancedStringSplit(self, s: str) -> int:
ans = l = 0
for c in s:
if c == 'L':
l += 1
else:
l -= 1
if l == 0:
ans += 1
return ans


• func balancedStringSplit(s string) int {
ans, l := 0, 0
for _, c := range s {
if c == 'L' {
l++
} else {
l--
}
if l == 0 {
ans++
}
}
return ans
}

• /**
* @param {string} s
* @return {number}
*/
var balancedStringSplit = function (s) {
let ans = 0;
let l = 0;
for (let c of s) {
if (c == 'L') {
++l;
} else {
--l;
}
if (l == 0) {
++ans;
}
}
return ans;
};