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1220.cpp
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1220.cpp
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__________________________________________________________________________________________________
sample 4 ms submission
class Solution {
public:
int countVowelPermutation(int n) {
long a = 1, e = 1, i = 1, o = 1, u = 1;
long mod = 1000000007;
for(int j = 1; j < n; ++j) {
long na = (e + i + u) % mod;
long ne = (a + i) % mod;
long ni = (e + o) % mod;
long no = i;
long nu = (i + o) % mod;
a = na;
e = ne;
i = ni;
o = no;
u = nu;
}
return (a + e + i + o + u) % mod;
}
};
__________________________________________________________________________________________________
sample 8 ms submission
class Solution {
public:
int countVowelPermutation(int n) {
typedef long long int LL;
LL f[5][20005];
LL P = 1e9 + 7;
// a=0, e=1, i=2, o=3, u=4
f[0][0] = f[1][0] = f[2][0] = f[3][0] = f[4][0] = 1;
for (int i = 1; i < n; i++) {
// e/i/u + a
f[0][i] = (f[1][i-1] + f[2][i-1] + f[4][i-1]) % P;
// a/i + e
f[1][i] = (f[0][i-1] + f[2][i-1]) % P;
// e/o + i
f[2][i] = (f[1][i-1] + f[3][i-1]) % P;
// i + o
f[3][i] = f[2][i-1] % P;
// i/o + u
f[4][i] = (f[2][i-1] + f[3][i-1]) % P;
}
return (f[0][n-1] + f[1][n-1] + f[2][n-1] + f[3][n-1] + f[4][n-1]) % P;
}
};
__________________________________________________________________________________________________
sample 12 ms submission
constexpr int MOD = 1000000007;
class Solution {
public:
int countVowelPermutation(int n) {
vector<vector<long long>> f(2, vector<long long>(5));
for (int i = 0; i < 5; ++ i) {
f[0][i] = 1;
}
for (int i = 1; i < n; ++ i) {
int x = i & 1;
for (int j = 0; j < 5; ++ j) {
f[x][j] = 0;
}
f[x][1] += f[1 - x][0];
f[x][0] += f[1 - x][1];
f[x][2] += f[1 - x][1];
f[x][0] += f[1 - x][2];
f[x][1] += f[1 - x][2];
f[x][3] += f[1 - x][2];
f[x][4] += f[1 - x][2];
f[x][2] += f[1 - x][3];
f[x][4] += f[1 - x][3];
f[x][0] += f[1 - x][4];
for (int j = 0; j < 5; ++ j) {
f[x][j] %= MOD;
}
}
long long ans = 0;
for (int j = 0; j < 5; ++ j) {
ans = (ans + f[(n - 1) & 1][j]) % MOD;
}
return (int)ans;
}
};