LeetCode in Kotlin
726. Number of Atoms
Hard
Given a string formula representing a chemical formula, return the count of each atom.
The atomic element always starts with an uppercase character, then zero or more lowercase letters, representing the name.
One or more digits representing that element’s count may follow if the count is greater than 1. If the count is 1, no digits will follow.
- For example,
"H2O"and"H2O2"are possible, but"H1O2"is impossible.
Two formulas are concatenated together to produce another formula.
- For example,
"H2O2He3Mg4"is also a formula.
A formula placed in parentheses, and a count (optionally added) is also a formula.
- For example,
"(H2O2)"and"(H2O2)3"are formulas.
Return the count of all elements as a string in the following form: the first name (in sorted order), followed by its count (if that count is more than 1), followed by the second name (in sorted order), followed by its count (if that count is more than 1), and so on.
The test cases are generated so that all the values in the output fit in a 32-bit integer.
Example 1:
Input: formula = “H2O”
Output: “H2O”
Explanation: The count of elements are {‘H’: 2, ‘O’: 1}.
Example 2:
Input: formula = “Mg(OH)2”
Output: “H2MgO2”
Explanation: The count of elements are {‘H’: 2, ‘Mg’: 1, ‘O’: 2}.
Example 3:
Input: formula = “K4(ON(SO3)2)2”
Output: “K4N2O14S4”
Explanation: The count of elements are {‘K’: 4, ‘N’: 2, ‘O’: 14, ‘S’: 4}.
Constraints:
1 <= formula.length <= 1000formulaconsists of English letters, digits,'(', and')'.formulais always valid.
Solution
class Solution {
data class Item(
var title: String = "",
var total: String = "",
var count: Int = 0
) {
fun getT(): String {
return if (total == "") "1" else total
}
}
fun countOfAtoms(formula: String): String {
val set = arrayListOf<Item>()
var current = Item()
var open = 0
var multiply = false
var multiplier = ""
fun multiplySet() {
if (multiplier == "") {
return
}
set.forEach {
if (it.count > open) {
it.total = (it.getT().toInt() * multiplier.toInt()).toString()
it.count -= 1
}
}
multiply = false
multiplier = ""
}
formula.forEach {
if (it !in '0'..'9') {
multiplySet()
}
when (it) {
in 'A'..'Z' -> {
current = Item()
set.add(current)
current.title = it.toString()
current.count = open
multiply = false
}
in 'a'..'z' -> {
current.title += it.toString()
}
'(' -> {
open++
}
')' -> {
multiply = true
open--
}
in '0'..'9' -> {
if (multiply) {
multiplier += it.toString()
} else {
current.total += it.toString()
}
}
}
}
if (multiply) {
multiplySet()
}
var result = ""
set.groupBy { it.title }.toSortedMap().forEach {
var count = 0
it.value.forEach { v ->
count += v.getT().toInt()
}
val c = if (count <= 1) "" else count.toString()
result += "${it.key}$c"
}
return result
}
}