1341. Split a String in Balanced Strings

Problem

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.

Solution

/**
 * @param {string} s
 * @return {number}
 */
var balancedStringSplit = function(s) {
    var num = 0;
    var S = 0;
    var L = 0;
    for (var i = 0; i < s.length; i++) {
        if (s[i] === 'L') {
            L++;
        } else {
            S++;
        }
        if (S === L) {
            num++;
            S = 0;
            L = 0;
        }
    }
    return num;
};

Explain:

Every time you meet a balanced string, split it.

Complexity:

• Time complexity : O(n).
• Space complexity : O(1).