http://codeforces.com/contest/1065/problem/E
数学推导题
1 #include <bits/stdc++.h> 2 using namespace std; 3 #define ll long long 4 #define minv 1e-6 5 #define inf 1e9 6 #define pi 3.1415926536 7 #define nl 2.7182818284 8 const ll mod=998244353; 9 const int maxn=1e5+10; 10 11 ll mul(ll a,ll b) 12 { 13 ll y=1; 14 while (b) 15 { 16 if (b & 1) 17 y=y*a%mod; 18 b>>=1; 19 a=a*a%mod; 20 } 21 return y; 22 } 23 24 int main() 25 { 26 int n,m,g,b,preb,len,i; 27 ll sum=1,v; 28 scanf("%d%d%d",&n,&m,&g); 29 preb=0; 30 for (i=1;i<=m;i++) 31 { 32 scanf("%d",&b); 33 len=b-preb; 34 v=mul(g,len); 35 sum=(sum*v%mod*(v+1)%mod*499122177)%mod; 36 preb=b; 37 } 38 v=mul(g,n-2*b); 39 sum=sum*v%mod; 40 cout<<sum; 41 return 0; 42 }