【DP】 ACdream 1412 2-3 Trees

简单DP。。。

#include <iostream>  #include <queue>  #include <stack>  #include <map>  #include <set>  #include <bitset>  #include <cstdio>  #include <algorithm>  #include <cstring>  #include <climits>#include <cstdlib>#include <cmath>#include <time.h>#define maxn  10005#define maxm 300005#define eps 1e-10//#define mod 1315423911#define INF 1e17#define lowbit(x) (x&(-x))#define mp make_pair#define ls o<<1#define rs o<<1 | 1#define lson o<<1, L, mid  #define rson o<<1 | 1, mid+1, R  typedef long long LL;typedef unsigned long long ULL;//typedef int LL;using namespace std;LL qpow(LL a, LL b){LL res=1,base=a;while(b){if(b%2)res=res*base;base=base*base;b/=2;}return res;}//LL powmod(LL a, LL b){LL res=1,base=a;while(b){if(b%2)res=res*base%mod;base=base*base%mod;b/=2;}return res;}void scanf(int &__x){__x=0;char __ch=getchar();while(__ch==' '||__ch=='\n')__ch=getchar();while(__ch>='0'&&__ch<='9')__x=__x*10+__ch-'0',__ch = getchar();}LL gcd(LL _a, LL _b){if(!_b) return _a;else return gcd(_b, _a%_b);}// headLL dp[maxn << 2];LL c[2][maxn];int n, mod;void init(void){memset(dp, 0, sizeof dp);memset(c, 0, sizeof c);}void work(void){int now = 0;dp[1] = 1;c[0][0] = c[0][1] = 1;for(int i = 1; i <= n; i++) {for(int j = 0; j <= i; j++) {int t1 = j*2, t2 = (i - j) * 3;dp[t1 + t2] = (dp[t1 + t2] + c[now][j] * dp[i]) % mod;}for(int j = 1; j <= i; j++) c[now^1][j] = (c[now][j] + c[now][j-1]) % mod;c[now^1][0] = c[now^1][i+1] = 1;now = now^1;}printf("%lld\n", dp[n]);}int main(void){while(scanf("%d%d", &n, &mod)!=EOF) {init();work();}return 0;}