hdu 4655——Cut Pieces

這代碼寫的很搓，但是。。賽後證明思路是正確的，就是maxn一直設到500000，結果一直wa。賽後發現只要到600000就可以ac。

 經驗不足啊。

 

#include<iostream>#include<algorithm>using namespace std;#define maxn 1000000#define mod 1000000007#define LL __int64#define ls (rt<<1)#define rs (rt<<1|1)#define mid ((t[rt].l+t[rt].r)>>1)LL a[maxn];struct tree{LL l,r;LL mul;}t[maxn<<2];bool cmp(LL a,LL b){return a>b;}void pushup(LL rt){t[rt].mul=(t[ls].mul*t[rs].mul)%mod;}void build(LL rt,LL l,LL r){t[rt].l=l,t[rt].r=r;if(l==r){t[rt].mul=a[l];return ;}build(ls,l,mid);build(rs,mid+1,r);pushup(rt);}LL query(LL rt,LL l,LL r){if(t[rt].l==l&&t[rt].r==r)return t[rt].mul;if(r<=mid)return query(ls,l,r)%mod;else if(l>mid)return query(rs,l,r)%mod;elsereturn (query(ls,l,mid)*query(rs,mid+1,r))%mod;}int main(){LL t;LL n;cin>>t;while(t--){scanf("%I64d",&n);if(n<=0){printf("0\n");continue;}LL k=1;for(LL i=1;i<=n;i++){scanf("%I64d",&a[i]);k=(k*a[i])%mod;}sort(a+1,a+1+n,cmp);LL ans=k;build(1,1,n);LL temp;for(LL i=1;i<=n-1;i++){if((i+1)/2-1>=1&&(i+1)/2+1<=n)temp=(query(1,1,(i+1)/2-1)*query(1,(i+1)/2+1,n))%mod;else{if(((i+1)/2)==1)temp=query(1,(i+1)/2+1,n);else if(((i+1)/2)==n)temp=query(1,1,(i+1)/2-1);else{temp=(query(1,1,(i+1)/2-1)*query(1,(i+1)/2+1,n))%mod;}}ans=(ans+(a[(i+1)/2]-1)*temp)%mod;}printf("%I64d\n",ans);}return 0;}