gym 100430 G【贪心+map瞎搞】

题意：

给你N个东西，其中任意两种东西可以合成。
问你最多可以合成多少东西。
在最多合成东西的情况下，要使得字典序最小。

思路：

先按照贪心的方法构造出字典序列最优的解。
然后有可能有一个剩下了一些的数量的东西（也可能没有）
那么就按照字典序从后往前扫，强行将最后的几对拆开来和剩余的匹配。

#include <cstdio>#include <cstring>#include <algorithm>#include <vector>#include <iostream>#include <map>#define MAXN 100005using namespace std;typedef long long ll;map< pair<int, int>, long long > Ans;map< pair<int, int> , long long, greater< pair<int, int> > > Res;long long a[MAXN];int n;void update(int x, int y, ll z){    if(z == 0) return;    if(Ans.find(make_pair(x,y)) != Ans.end()) Ans[make_pair(x,y)] += z;    else Ans[make_pair(x,y)] = z;}int main(){    freopen("magic.in", "r", stdin);    freopen("magic.out", "w", stdout);    cin>>n;    for(int i=1; i<=n; i++)        cin>>a[i];    Ans.clear();    Res.clear();    for(int i=1; i<=n; i++)        for(int j=i+1; j<=n && a[i]>0; j++)        {            ll siz = min(a[i],a[j]);            if(siz == 0) continue;            if(Res.find(make_pair(i,j)) != Res.end()) Res[make_pair(i,j)] += siz;            else Res[make_pair(i,j)] = siz;            a[i] -= siz;            a[j] -= siz;        }    int remain_id = -1;    ll remain_num = 0;    for(int i=1; i<=n; i++)        if(a[i] > 0)        {            remain_id = i;            break;        }    if(remain_id!=-1)        remain_num = a[remain_id]/2;    else        remain_num = 0;    for(auto it: Res)    {        int i = it.first.first, j = it.first.second, ff, ee;        ll res = it.second;        if(i != remain_id && j != remain_id)        {            if(remain_num != 0)            {                ll siz = min(res, remain_num);                ff = min(remain_id, i), ee = max(remain_id, i);                update(ff, ee, siz);                ff = min(remain_id, j), ee = max(remain_id, j);                update(ff, ee, siz);                update(i, j, res - siz);                remain_num -= siz;            }            else            {                update(i, j, res);            }        }        else        {            update(i, j, res);        }    }    cout<<Ans.size()<<endl;    for(auto it: Ans)    {        cout<<it.first.first<<" "<<it.first.second<<" "<<it.second<<endl;    }    return 0;}

//      whn6325689//      Mr.Phoebe//      http://blog.csdn.net/u013007900#include <algorithm>#include <iostream>#include <iomanip>#include <cstring>#include <climits>#include <complex>#include <fstream>#include <cassert>#include <cstdio>#include <bitset>#include <vector>#include <deque>#include <queue>#include <stack>#include <ctime>#include <set>#include <map>#include <cmath>#include <functional>#include <numeric>#pragma comment(linker, "/STACK:1024000000,1024000000")using namespace std;#define eps 1e-9#define PI acos(-1.0)#define INF 0x3f3f3f3f#define LLINF 1LL<<62#define speed std::ios::sync_with_stdio(false);typedef long long ll;typedef unsigned long long ull;typedef long double ld;typedef pair<ll, ll> pll;typedef complex<ld> point;typedef pair<int, int> pii;typedef pair<pii, int> piii;typedef vector<int> vi;#define CLR(x,y) memset(x,y,sizeof(x))#define CPY(x,y) memcpy(x,y,sizeof(x))#define clr(a,x,size) memset(a,x,sizeof(a[0])*(size))#define cpy(a,x,size) memcpy(a,x,sizeof(a[0])*(size))#define debug(a) cout << #a" = " << (a) << endl;#define debugarry(a, n) for (int i = 0; i < (n); i++) { cout << #a"[" << i << "] = " << (a)[i] << endl; }#define mp(x,y) make_pair(x,y)#define pb(x) push_back(x)#define lowbit(x) (x&(-x))#define MID(x,y) (x+((y-x)>>1))#define getidx(l,r) (l+r | l!=r)#define ls getidx(l,mid)#define rs getidx(mid+1,r)#define lson l,mid#define rson mid+1,rtemplate<class T>inline bool read(T &n){    T x = 0, tmp = 1;    char c = getchar();    while((c < '0' || c > '9') && c != '-' && c != EOF) c = getchar();    if(c == EOF) return false;    if(c == '-') c = getchar(), tmp = -1;    while(c >= '0' && c <= '9') x *= 10, x += (c - '0'),c = getchar();    n = x*tmp;    return true;}template <class T>inline void write(T n){    if(n < 0)    {        putchar('-');        n = -n;    }    int len = 0,data[20];    while(n)    {        data[len++] = n%10;        n /= 10;    }    if(!len) data[len++] = 0;    while(len--) putchar(data[len]+48);}//-----------------------------------const int MAXN=100010;map<pii,ll> Ans,Res;int a[MAXN],n;int main(){    freopen("magic.in", "r", stdin);    freopen("magic.out", "w", stdout);    cin>>n;    for(int i=1;i<=n;i++)        cin>>a[i];    Ans.clear();    Res.clear();    for(int i=1;i<=n;i++)        for(int j=i+1;j<=n && a[i]>0;j++)        {            if(a[j]==0) continue;            ll siz=min(a[i],a[j]);            Res[mp(i,j)]+=siz;            a[i]-=siz;a[j]-=siz;        }    int remain_id=-1;    ll remain_num=0;    for(int i=1;i<=n;i++)    if(a[i]>0)    {        remain_id=i;        break;    }    if(remain_id!=-1)        remain_num=a[remain_id]/2;    else        remain_num=0;    for(map<pii,ll>::reverse_iterator it=Res.rbegin();it!=Res.rend();it++)    {        int i=it->first.first,j=it->first.second,ff,ee;        ll res=it->second;        if(i!=remain_id && j!=remain_id)        {            if(remain_num>res)            {                ll siz=res;                ff=min(remain_id,i),ee=max(remain_id,i);                Ans[mp(ff,ee)]+=siz;                ff=min(remain_id,j),ee=max(remain_id,j);                Ans[mp(ff,ee)]+=siz;                remain_num-=siz;            }            else if(remain_num!=0)            {                ll siz=remain_num;                ff=min(remain_id,i),ee=max(remain_id,i);                Ans[mp(ff,ee)]+=siz;                ff=min(remain_id,j),ee=max(remain_id,j);                Ans[mp(ff,ee)]+=siz;                if(res!=siz)                    Ans[mp(i,j)]+=res-siz;                remain_num=0;            }            else            {                Ans[mp(i,j)]+=res;            }        }        else            Ans[mp(i,j)]+=res;    }    cout<<Ans.size()<<endl;    for(auto it:Ans)    {        cout<<it.first.first<<" "<<it.first.second<<" "<<it.second<<endl;    }    return 0;}