HDU 5813 Elegant Construction

构造。从a[i]最小的开始放置，例如放置了a[p]，那么还未放置的，还需要建边的那个点 需求量-1，然后把边连起来。

#pragma comment(linker, "/STACK:1024000000,1024000000")

#include<cstdio>

#include<cstring>

#include<cmath>

#include<algorithm>

#include<vector>

#include<map>

#include<set>

#include<queue>

#include<stack>

#include<iostream>

using namespace std;

typedef long long LL;

const double pi=acos(-1.0),eps=1e-;

void File()

{

    freopen("D:\\in.txt","r",stdin);

    freopen("D:\\out.txt","w",stdout);

}

inline int read()

{

    char c = getchar(); while(!isdigit(c)) c = getchar(); int x = ;

    while(isdigit(c)) { x = x *  + c - ''; c = getchar();  }

    return x;

}

const int maxn=+;

int T,n,sz;

struct X{int f,num; }s[maxn],ans[maxn*maxn];

bool cmp(X a, X b) {return a.num<b.num; }

int main()

{

    scanf("%d",&T); int cas=;

    while(T--)

    {

        scanf("%d",&n); sz=;

        for(int i=;i<=n;i++) { scanf("%d",&s[i].num); s[i].f=i; }

        sort(s+,s++n,cmp);

        bool fail=;

        for(int i=;i<=n;i++)

        {

            if(s[i].num!=) { fail=; break; }

            for(int j=i+;j<=n;j++)

            {

                if(s[j].num==) continue;

                ans[sz].f=s[i].f; ans[sz].num=s[j].f;  sz++; s[j].num--;

            }

        }

        printf("Case #%d: ",cas++);

        if(fail==) { printf("No\n");  continue; }

        else printf("Yes\n");

        printf("%d\n",sz);

        for(int i=;i<sz;i++) printf("%d %d\n",ans[i].num,ans[i].f);

    }

    return ;

}