|
| 1 | +//DP |
| 2 | +classSolution { |
| 3 | +funcountVowelPermutation(n:Int):Int { |
| 4 | +val mod=1_000_000_000+7 |
| 5 | +val dp=Array (n+1) {LongArray (5) } |
| 6 | + |
| 7 | +for (jin0 until5) |
| 8 | + dp[1][j]=1 |
| 9 | + |
| 10 | +val a=0 |
| 11 | +val e=1 |
| 12 | +val i=2 |
| 13 | +val o=3 |
| 14 | +val u=4 |
| 15 | + |
| 16 | +for (jin2..n) { |
| 17 | + dp[j][a]=0L+ (dp[j-1][e]+ dp[j-1][i]+ dp[j-1][u])% mod |
| 18 | + dp[j][e]=0L+ (dp[j-1][a]+ dp[j-1][i])% mod |
| 19 | + dp[j][i]=0L+ (dp[j-1][e]+ dp[j-1][o])% mod |
| 20 | + dp[j][o]=0L+ (dp[j-1][i])% mod |
| 21 | + dp[j][u]=0L+ (dp[j-1][i]+ dp[j-1][o])% mod |
| 22 | + } |
| 23 | + |
| 24 | +return (dp[n].sum()!!% mod).toInt() |
| 25 | + } |
| 26 | +} |
| 27 | + |
| 28 | +//recursion + memoization |
| 29 | +classSolution { |
| 30 | +funcountVowelPermutation(n:Int):Int { |
| 31 | +val mod=1_000_000_000+7 |
| 32 | +val dp=Array (n) {IntArray (5) {-1 } } |
| 33 | + |
| 34 | +val a=0 |
| 35 | +val e=1 |
| 36 | +val i=2 |
| 37 | +val o=3 |
| 38 | +val u=4 |
| 39 | + |
| 40 | +val follow=mapOf( |
| 41 | + a tolistOf(e), |
| 42 | + e tolistOf(a, i), |
| 43 | + i tolistOf(a, e, o, u), |
| 44 | + o tolistOf(i, u), |
| 45 | + u tolistOf(a) |
| 46 | + ) |
| 47 | + |
| 48 | +fundfs(idx:Int,prev:Int):Int { |
| 49 | +if (idx== n)return1 |
| 50 | +if (dp[idx][prev]!=-1)return dp[idx][prev] |
| 51 | + |
| 52 | +var res=0 |
| 53 | + follow[prev]?.forEach { |
| 54 | + res= (res+ dfs(idx+1, it))% mod |
| 55 | + } |
| 56 | + |
| 57 | + dp[idx][prev]= res |
| 58 | +return res |
| 59 | + } |
| 60 | + |
| 61 | +var res=0 |
| 62 | + follow.keys.forEach { |
| 63 | + res= (res+ dfs(1, it))% mod |
| 64 | + } |
| 65 | + |
| 66 | +return res |
| 67 | + } |
| 68 | +} |