gym 100430 G【贪心+map瞎搞】

Myth丶恋晨 2022-08-09 00:50 7阅读 0赞

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 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;
    }

// 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;
    }