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763. Partition Labels

Medium

You are given a string s. We want to partition the string into as many parts as possible so that each letter appears in at most one part.

Return a list of integers representing the size of these parts.

Example 1:

Input: s = “ababcbacadefegdehijhklij”

Output: [9,7,8]

Explanation:

The partition is "ababcbaca", "defegde", "hijhklij".
This is a partition so that each letter appears in at most one part.
A partition like "ababcbacadefegde", "hijhklij" is incorrect, because it splits s into less parts. 

Example 2:

Input: s = “eccbbbbdec”

Output: [10]

Constraints:

• 1 <= s.length <= 500
• s consists of lowercase English letters.

Solution

object Solution {
    def partitionLabels(s: String): List[Int] = {
        val letters = s.toCharArray
        val result = new scala.collection.mutable.ListBuffer[Int]()
        val position = new Array[Int](26)

        for (i <- 0 until letters.length) {
            position(letters(i) - 'a') = i
        }

        var i = 0
        var prev = -1
        var max = 0

        while (i < letters.length) {
            if (position(letters(i) - 'a') > max) {
                max = position(letters(i) - 'a')
            }
            if (i == max) {
                result += (i - prev)
                prev = i
            }
            i += 1
        }

        result.toList
    }
}

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