BZOJ 1037 生日聚会(神DP)

这题的DP很难想，定义dp[i][j][a][b]表示用了i个男生，j个女生，任一连续的后缀区间内，男生比女生最多多a人，女生比男生最多多b人。

转移就是显然了。

# include <cstdio>
# include <cstring>
# include <cstdlib>
# include <iostream>
# include <vector>
# include <queue>
# include <stack>
# include <map>
# include <set>
# include <cmath>
# include <algorithm>
using namespace std;
# define lowbit(x) ((x)&(-x))
# define pi acos(-1.0)
# define eps 1e-
# define MOD
# define INF
# define mem(a,b) memset(a,b,sizeof(a))
# define FOR(i,a,n) for(int i=a; i<=n; ++i)
# define FO(i,a,n) for(int i=a; i<n; ++i)
# define bug puts("H");
# define lch p<<,l,mid
# define rch p<<|,mid+,r
# define mp make_pair
# define pb push_back
typedef pair<int,int> PII;
typedef vector<int> VI;
# pragma comment(linker, "/STACK:1024000000,1024000000")
typedef long long LL;
int Scan() {
    int res=, flag=;
    char ch;
    if((ch=getchar())=='-') flag=;
    else if(ch>=''&&ch<='') res=ch-'';
    while((ch=getchar())>=''&&ch<='')  res=res*+(ch-'');
    return flag?-res:res;
}
void Out(int a) {
    if(a<) {putchar('-'); a=-a;}
    if(a>=) Out(a/);
    putchar(a%+'');
}
const int N=;
//Code begin...

int dp[][][][];

int main ()
{
    int n, m, k;
    scanf("%d%d%d",&n,&m,&k);
    dp[][][][]=;
    FOR(i,,n) FOR(j,,m) FOR(l1,,k) FOR(l2,,k) {
        dp[i+][j][l1+][max(l2-,)]=(dp[i+][j][l1+][max(l2-,)]+dp[i][j][l1][l2])%MOD;
        dp[i][j+][max(l1-,)][l2+]=(dp[i][j+][max(l1-,)][l2+]+dp[i][j][l1][l2])%MOD;
    }
    int ans=;
    FOR(i,,k) FOR(j,,k) ans=(ans+dp[n][m][i][j])%MOD;
    printf("%d\n",ans);
    return ;
}