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。

[code]#include <cstdio>
#include <cstring>
#include <algorithm>
#include <vector>
#include <iostream>
#include <map>
#define MAXN 100005

using 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;
}

[code]//      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,r

template<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;
}