题意:给定n个物品,其中i,j必选,l,m必不选,问组成体积为s的方法一共有多少种
思路:定义dp[i][j][s1][s2],表示前i种物品能够构成的体积为j,其中有s1种定为必选,s2种定为不必选;因为递推到第i层时,只与第i-1层有关,所以把第一维降到2来省内存。然后就是dp[i][j][s1][s2]=dp[i-1][j][s1][s2]+dp[i-1][j][s1][s2-1]+dp[i-1][j-a[i]][s1-1][s2]+dp[i-1][j-a[i]][s1][s2];然后就是对i,j,l,m排序了,A(2,2)*A(2,2)
/************************************************************** Problem:hdu 5800 To My Girlfriend User: youmi Language: C++ Result: Accepted Time:1903MS Memory:1716K ****************************************************************/ //#pragma comment(linker, "/STACK:1024000000,1024000000") //#include<bits/stdc++.h> #include <iostream> #include <cstdio> #include <cstring> #include <algorithm> #include <map> #include <stack> #include <set> #include <sstream> #include <cmath> #include <queue> #include <deque> #include <string> #include <vector> #define zeros(a) memset(a,0,sizeof(a)) #define ones(a) memset(a,-1,sizeof(a)) #define sc(a) scanf("%d",&a) #define sc2(a,b) scanf("%d%d",&a,&b) #define sc3(a,b,c) scanf("%d%d%d",&a,&b,&c) #define scs(a) scanf("%s",a) #define sclld(a) scanf("%I64d",&a) #define pt(a) printf("%d\n",a) #define ptlld(a) printf("%I64d\n",a) #define rep(i,from,to) for(int i=from;i<=to;i++) #define irep(i,to,from) for(int i=to;i>=from;i--) #define Max(a,b) ((a)>(b)?(a):(b)) #define Min(a,b) ((a)<(b)?(a):(b)) #define lson (step<<1) #define rson (lson+1) #define eps 1e-6 #define oo 0x3fffffff #define TEST cout<<"*************************"<<endl const double pi=4*atan(1.0); using namespace std; typedef long long ll; template <class T> inline void read(T &n) { char c; int flag = 1; for (c = getchar(); !(c >= ‘0‘ && c <= ‘9‘ || c == ‘-‘); c = getchar()); if (c == ‘-‘) flag = -1, n = 0; else n = c - ‘0‘; for (c = getchar(); c >= ‘0‘ && c <= ‘9‘; c = getchar()) n = n * 10 + c - ‘0‘; n *= flag; } int Pow(int base, ll n, int mo) { if (n == 0) return 1; if (n == 1) return base % mo; int tmp = Pow(base, n >> 1, mo); tmp = (ll)tmp * tmp % mo; if (n & 1) tmp = (ll)tmp * base % mo; return tmp; } //*************************** int n,s; const int maxn=1000+10; const ll mod=1000000007; ll dp[2][maxn][3][3]; int a[maxn]; ll ans; int main() { #ifndef ONLINE_JUDGE freopen("in.txt","r",stdin); #endif int T_T; scanf("%d",&T_T); for(int kase=1;kase<=T_T;kase++) { sc2(n,s); rep(i,1,n) sc(a[i]); zeros(dp); ll ans=0; dp[0][0][0][0]=1; int temp=1; rep(i,1,n) { zeros(dp[temp]); rep(j,0,s) rep(s1,0,2) rep(s2,0,2) { dp[temp&1][j][s1][s2]=(dp[temp&1][j][s1][s2]+dp[temp^1][j][s1][s2])%mod; if(s2>=1) dp[temp&1][j][s1][s2]=(dp[temp&1][j][s1][s2]+dp[temp^1][j][s1][s2-1])%mod; if(s1>=1&&j>=a[i]) dp[temp&1][j][s1][s2]=(dp[temp&1][j][s1][s2]+dp[temp^1][j-a[i]][s1-1][s2])%mod; if(j>=a[i]) dp[temp&1][j][s1][s2]=(dp[temp&1][j][s1][s2]+dp[temp^1][j-a[i]][s1][s2])%mod; } temp^=1; } temp^=1; rep(j,1,s) ans=(ans+dp[temp][j][2][2])%mod; ans=(ans*4)%mod; ptlld(ans); } }
时间: 2024-10-10 10:01:22