LeetCode in Kotlin
402. Remove K Digits
Medium
Given string num representing a non-negative integer num, and an integer k, return the smallest possible integer after removing k digits from num.
Example 1:
Input: num = “1432219”, k = 3
Output: “1219”
Explanation: Remove the three digits 4, 3, and 2 to form the new number 1219 which is the smallest.
Example 2:
Input: num = “10200”, k = 1
Output: “200”
Explanation: Remove the leading 1 and the number is 200. Note that the output must not contain leading zeroes.
Example 3:
Input: num = “10”, k = 2
Output: “0”
Explanation: Remove all the digits from the number and it is left with nothing which is 0.
Constraints:
1 <= k <= num.length <= 105numconsists of only digits.numdoes not have any leading zeros except for the zero itself.
Solution
@Suppress("NAME_SHADOWING")
class Solution {
fun removeKdigits(num: String, k: Int): String {
var k = k
val list = CharArray(num.length)
val len = num.length - k
var top = 0
for (i in 0 until num.length) {
while (top > 0 && k > 0 && num[i] < list[top - 1]) {
top--
k--
}
list[top++] = num[i]
}
var number = 0
while (number < len && list[number] == '0') {
number++
}
return if (number == len) "0" else String(list, number, len - number)
}
}