01背包方案数（变种题）Stone game--The Preliminary Contest for ICPC Asia Shanghai 2019

题意：https://nanti.jisuanke.com/t/41420

给你n个石子的重量，要求满足（Sum<=2*sum<=Sum+min)的方案数，min是你手里的最小值。

思路：

从最大重量的石子开始背包，每次ans+=dp【j-v【i】】就行了。

 #define IOS ios_base::sync_with_stdio(0); cin.tie(0);
 #include <cstdio>//sprintf islower isupper
 #include <cstdlib>//malloc  exit strcat itoa system("cls")
 #include <iostream>//pair
 #include <fstream>//freopen("C:\\Users\\13606\\Desktop\\草稿.txt","r",stdin);
 #include <bitset>
 //#include <map>
 //#include<unordered_map>
 #include <vector>
 #include <stack>
 #include <set>
 #include <string.h>//strstr substr
 #include <string>
 #include <time.h>//srand(((unsigned)time(NULL))); Seed n=rand()%10 - 0~9;
 #include <cmath>
 #include <deque>
 #include <queue>//priority_queue<int, vector<int>, greater<int> > q;//less
 #include <vector>//emplace_back
 //#include <math.h>
 //#include <windows.h>//reverse(a,a+len);// ~ ! ~ ! floor
 #include <algorithm>//sort + unique : sz=unique(b+1,b+n+1)-(b+1);+nth_element(first, nth, last, compare)
 using namespace std;//next_permutation(a+1,a+1+n);//prev_permutation
 #define rint register int
 #define fo(a,b,c) for(rint a=b;a<=c;++a)
 #define fr(a,b,c) for(rint a=b;a>=c;--a)
 #define mem(a,b) memset(a,b,sizeof(a))
 #define pr printf
 #define sc scanf
 #define ls rt<<1
 #define rs rt<<1|1
 typedef long long ll;
 void swapp(int &a,int &b);
 double fabss(double a);
 int maxx(int a,int b);
 int minn(int a,int b);
 int Del_bit_1(int n);
 int lowbit(int n);
 int abss(int a);
 const double E=2.718281828;
 const double PI=acos(-1.0);
 //const ll INF=(1LL<<60);
 const int inf=(<<);
 const double ESP=1e-;
 const int mod=(int)1e9+;
 const int N=(int)1e6+;

 int v[N],dp[N];
 void Init(int _[],int n)
 {
     for(int i=;i<=n;++i)
         _[i]=;
 }

 void PR(int _[],int n)
 {
     for(int i=;i<=n;++i)
         pr("%d ",_[i]);
     pr("\n");
 }

 bool J(int sum,int x,int min_)
 {
     return *x>=sum&&*x<=sum+min_;
 }

 int main()
 {
     int T;
     sc("%d",&T);
     while(T--)
     {
         int n,sum=;
         sc("%d",&n);
         for(int i=;i<=n;++i)
             sc("%d",&v[i]),sum+=v[i];
         sort(v+,v++n);
         Init(dp,sum);

         ll ans=;
         dp[]=;
         for(int i=n;i>=;--i)
         {
             for(int j=sum;j>=v[i];--j)
                 if(dp[j-v[i]])
                 {
                     dp[j]+=dp[j-v[i]];
                     dp[j]%=mod;
                     ans+=J(sum,j,v[i])?dp[j-v[i]]:;
                     ans%=mod;
                 }
         }
         pr("%lld\n",ans);
     }
     return ;
 }

 /**************************************************************************************/

 int maxx(int a,int b)
 {
     return a>b?a:b;
 }

 void swapp(int &a,int &b)
 {
     a^=b^=a^=b;
 }

 int lowbit(int n)
 {
     return n&(-n);
 }

 int Del_bit_1(int n)
 {
     return n&(n-);
 }

 int abss(int a)
 {
     return a>?a:-a;
 }

 double fabss(double a)
 {
     return a>?a:-a;
 }

 int minn(int a,int b)
 {
     return a<b?a:b;
 }