#include <bits/stdc++.h>
using namespace std;
#define rep(i,a,n) for (int i=a;i<n;i++)
#define per(i,a,n) for (int i=n-1;i>=a;i--)
#define pb push_back
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
#define SZ(x) ((int)(x).size())
typedef vector<int> VI;
typedef long long ll;
typedef pair<int,int> PII;
typedef double db;
//mt19937 mrand(random_device{}());
ll mod;
//int rnd(int x) { return mrand() % x;}
ll powmod(ll a,ll b) {ll res=1;a%=mod; assert(b>=0); for(;b;b>>=1){if(b&1)res=res*a%mod;a=a*a%mod;}return res;}
int gcd(int a,int b) { return b?gcd(b,a%b):a;}
// head
const int N=1e7+5;
#define INF 0x3f3f3f3f
template<class T> inline void read(T &x) {
x=0; int c=getchar(),f=1;
for (;!isdigit(c);c=getchar()) if (c==45) f=-1;
for (;isdigit(c);c=getchar()) (x*=10)+=f*(c-'0');
}
int n,m,dp[2][N];
int main() {
read(n); read(m); read(mod);
int ans=0;
rep(i,0,n) {
int s=0;
rep(j,0,m)
if (i==0) dp[i%2][j]=j+1;
else {
dp[i%2][j]=0;
if (j!=0) {
dp[i%2][j]=(dp[i%2][j]+dp[i%2][j-1])%mod;
s=((s+dp[1-i%2][m-j])%mod-dp[1-i%2][j-1]+mod)%mod;
dp[i%2][j]=(dp[i%2][j]+s)%mod;
}
dp[i%2][j]=(dp[i%2][j]+1ll*(j+1)*dp[1-i%2][m-j-1]%mod)%mod;
}
}
rep(i,0,m) ans=(ans+dp[(n-1)%2][i])%mod;
printf("%d\n",ans);
}
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 | #include <bits/stdc++.h> using namespace std; #define rep(i,a,n) for (int i=a;i<n;i++) #define per(i,a,n) for (int i=n-1;i>=a;i--) #define pb push_back #define mp make_pair #define all(x) (x).begin(),(x).end() #define fi first #define se second #define SZ(x) ((int)(x).size()) typedef vector<int> VI; typedef long long ll; typedef pair<int,int> PII; typedef double db; //mt19937 mrand(random_device{}()); ll mod; //int rnd(int x) { return mrand() % x;} ll powmod(ll a,ll b) {ll res=1;a%=mod; assert(b>=0); for(;b;b>>=1){if(b&1)res=res*a%mod;a=a*a%mod;}return res;} int gcd(int a,int b) { return b?gcd(b,a%b):a;} // head const int N=1e7+5; #define INF 0x3f3f3f3f template<class T> inline void read(T &x) { x=0; int c=getchar(),f=1; for (;!isdigit(c);c=getchar()) if (c==45) f=-1; for (;isdigit(c);c=getchar()) (x*=10)+=f*(c-'0'); } int n,m,dp[2][N]; int main() { read(n); read(m); read(mod); int ans=0; rep(i,0,n) { int s=0; rep(j,0,m) if (i==0) dp[i%2][j]=j+1; else { dp[i%2][j]=0; if (j!=0) { dp[i%2][j]=(dp[i%2][j]+dp[i%2][j-1])%mod; s=((s+dp[1-i%2][m-j])%mod-dp[1-i%2][j-1]+mod)%mod; dp[i%2][j]=(dp[i%2][j]+s)%mod; } dp[i%2][j]=(dp[i%2][j]+1ll*(j+1)*dp[1-i%2][m-j-1]%mod)%mod; } } rep(i,0,m) ans=(ans+dp[(n-1)%2][i])%mod; printf("%d\n",ans); } |
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