LeetCode in Kotlin
1234. Replace the Substring for Balanced String
Medium
You are given a string s of length n containing only four kinds of characters: 'Q', 'W', 'E', and 'R'.
A string is said to be balanced if each of its characters appears n / 4 times where n is the length of the string.
Return the minimum length of the substring that can be replaced with any other string of the same length to make s balanced. If s is already balanced, return 0.
Example 1:
Input: s = “QWER”
Output: 0
Explanation: s is already balanced.
Example 2:
Input: s = “QQWE”
Output: 1
Explanation: We need to replace a ‘Q’ to ‘R’, so that “RQWE” (or “QRWE”) is balanced.
Example 3:
Input: s = “QQQW”
Output: 2
Explanation: We can replace the first “QQ” to “ER”.
Constraints:
n == s.length4 <= n <= 105nis a multiple of4.scontains only'Q','W','E', and'R'.
Solution
class Solution {
fun balancedString(s: String): Int {
val n = s.length
var ans = n
var excess = 0
val cnt = IntArray(128)
cnt['R'.code] = -n / 4
cnt['E'.code] = cnt['R'.code]
cnt['W'.code] = cnt['E'.code]
cnt['Q'.code] = cnt['W'.code]
for (ch in s.toCharArray()) {
if (++cnt[ch.code] == 1) {
excess++
}
}
if (excess == 0) {
return 0
}
var i = 0
var j = 0
while (i < n) {
if (--cnt[s[i].code] == 0) {
excess--
}
while (excess == 0) {
if (++cnt[s[j].code] == 1) {
excess++
}
ans = Math.min(i - j + 1, ans)
j++
}
i++
}
return ans
}
}