LeetCode in Kotlin
1223. Dice Roll Simulation
Hard
A die simulator generates a random number from 1 to 6 for each roll. You introduced a constraint to the generator such that it cannot roll the number i more than rollMax[i] (1-indexed) consecutive times.
Given an array of integers rollMax and an integer n, return the number of distinct sequences that can be obtained with exact n rolls. Since the answer may be too large, return it modulo 109 + 7.
Two sequences are considered different if at least one element differs from each other.
Example 1:
Input: n = 2, rollMax = [1,1,2,2,2,3]
Output: 34
Explanation: There will be 2 rolls of die, if there are no constraints on the die, there are 6 * 6 = 36 possible combinations. In this case, looking at rollMax array, the numbers 1 and 2 appear at most once consecutively, therefore sequences (1,1) and (2,2) cannot occur, so the final answer is 36-2 = 34.
Example 2:
Input: n = 2, rollMax = [1,1,1,1,1,1]
Output: 30
Example 3:
Input: n = 3, rollMax = [1,1,1,2,2,3]
Output: 181
Constraints:
1 <= n <= 5000rollMax.length == 61 <= rollMax[i] <= 15
Solution
class Solution {
fun dieSimulator(n: Int, rollMax: IntArray): Int {
val all = Array(6) { LongArray(15 + 1) }
val countsBySide = LongArray(6)
var total: Long = 0
var newTotal: Long
var max: Int
for (j in all.indices) {
all[j][1] = 1
countsBySide[j] = 1
total = 6
}
for (i in 1 until n) {
newTotal = total
for (j in all.indices) {
all[j][0] = (total - countsBySide[j]) % MOD
max = rollMax[j]
newTotal = newTotal - all[j][max] + all[j][0]
countsBySide[j] = (total - all[j][max]) % MOD
System.arraycopy(all[j], 0, all[j], 1, max)
}
total = newTotal
}
return (total % MOD).toInt()
}
companion object {
private const val MOD: Long = 1000000007
}
}