poj 2365 Find a multiple

组合数学例题，给你n个正整数总能选出几个使它们的和 mod n == 0

#include<iostream>#include<vector>#include<algorithm>#include<cstdio>#include<queue>#include<stack>#include<string>#include<map>#include<set>#include<cmath>#include<cassert>#include<cstring>#include<iomanip>using namespace std;#ifdef _WIN32#define i64 __int64#define out64 "%I64d\n"#define in64 "%I64d"#else#define i64 long long#define out64 "%lld\n"#define in64 "%lld"#endif/************ for topcoder by zz1215 *******************/#define FOR(i,a,b)      for( int i = (a) ; i <= (b) ; i ++)#define FFF(i,a)        for( int i = 0 ; i < (a) ; i ++)#define FFD(i,a,b)      for( int i = (a) ; i >= (b) ; i --)#define S64(a)          scanf(in64,&a)#define SS(a)           scanf("%d",&a)#define LL(a)           ((a)<<1)#define RR(a)           (((a)<<1)+1)#define pb              push_back#define CL(Q)           while(!Q.empty())Q.pop()#define MM(name,what)   memset(name,what,sizeof(name))#define MC(a,b)memcpy(a,b,sizeof(b))#define MAX(a,b)        ((a)>(b)?(a):(b))#define MIN(a,b)        ((a)<(b)?(a):(b))#define read            freopen("in.txt","r",stdin)#define write           freopen("out.txt","w",stdout)const int inf = 0x3f3f3f3f;const i64 inf64 = 0x3f3f3f3f3f3f3f3fLL;const double oo = 10e9;const double eps = 10e-9;const double pi = acos(-1.0);const int maxn = 10011;int a[maxn];int s[maxn];int n;int f[maxn];int main(){while(cin>>n){for(int i=0;i<=n;i++){f[i]=-1;}for(int i=1;i<=n;i++){cin>>a[i];}f[0]=s[0]=0;for(int i=1;i<=n;i++){s[i]=s[i-1]+a[i];s[i]%=n;if(f[s[i]]!=-1){cout<<i-f[s[i]]<<endl;for(int j=f[s[i]]+1;j<=i;j++){cout<<a[j]<<endl;}break;}else{f[s[i]]=i;}}}return 0;}