POJ-1011 sticks 棍棒拼接

#include<stdio.h>
#include<string.h>
#include<algorithm>
#include<math.h>
#include<iostream>
#include<stdlib.h>
#include<set>
#include<map>
#include<queue>
#include<vector>
#include<bitset>
#pragma comment(linker, "/STACK:1024000000,1024000000")
template <class T>
bool scanff(T &ret){ //Faster Input
char c; int sgn; T bit=0.1;
if(c=getchar(),c==EOF) return 0;
while(c!='-'&&c!='.'&&(c<'0'||c>'9')) c=getchar();
sgn=(c=='-')?-1:1;
ret=(c=='-')?0:(c-'0');
while(c=getchar(),c>='0'&&c<='9') ret=ret*10+(c-'0');
if(c==' '||c=='\n'){ ret*=sgn; return 1; }
while(c=getchar(),c>='0'&&c<='9') ret+=(c-'0')*bit,bit/=10;
ret*=sgn;
return 1;
}
#define inf 1073741823
#define llinf 4611686018427387903LL
#define PI acos(-1.0)
#define lth (th<<1)
#define rth (th<<1|1)
#define rep(i,a,b) for(int i=a;i<=b;i++)
#define drep(i,a,b) for(int i=a;i>=b;i--)
#define gson(i,root) for(int i=ptx[root];~i;i=ed[i].next)
#define tdata int testnum;scanff(testnum);for(int cas=1;cas<=testnum;cas++)
#define mem(x,val,n) memset(x,val,(n+2)*sizeof(x[0]))
#define mkp(a,b) make_pair(a,b)
#define findx(x) lower_bound(b+1,b+1+bn,x)-b
#define pb(x) push_back(x)
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;

int a[1111],n,len,tot,lnum;
bool cmp(int x,int y){return x>y;}
bool vis[1111];
int last;
bool dfs(int r,int need){
if(r==0&&need==0)return true;
if(need==0)need=len;
rep(i,(need==len)?1:last+1,n){//优化起始位置，直接从上一根接下去匹配
if(i>1&&a[i]==a[i-1]&&vis[i-1]==false)continue;
//如果这个位置这个长度的棍子已经匹配失败过，跳过这个棍子
if(!vis[i]&&a[i]<=need){
vis[i]=true;last=i;
if(dfs(r-1,need-a[i]))return true;
else{
vis[i]=false;
if(a[i]==need||need==len)return false;
//如果第一根或者最后一根匹配失败，说明已经不可能[只要这个剪枝就能AC]
}
}
}
return false;
}

main(){
while(scanf("%d",&n)!=EOF){
if(n==0)break;
int sum=0;
rep(i,1,n){
scanff(a[i]);
sum+=a[i];
}
sort(a+1,a+1+n,cmp);
mem(vis,0,n);
rep(i,1,sum){
if(sum%i==0){
len=i;
lnum=sum/i;
if(dfs(n,len)){
printf("%d\n",i);
break;
}
}
}
}
}