sgu 138 分类： sgu 2015-03-16 18:32 40人阅读 评论(0) 收藏

构造题

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构造。构造的关键是：1.每场的胜者将在下一场出现 2.不会自己对战自己 

按如下方法构造： 

按场次从大到小填掉win，若只剩一场就填到lose去。 

win   a  a  a  b  b  c  c  … 

lose           a     b 

最后把剩下的填到lose没填的地方即可。

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nocow

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#include<cstdio>
#include<cstdlib>
#include<ctime>
#include<cmath>
#include<iostream>
#include<algorithm>

const int MAXN = 105;

int n;
int cnt[MAXN] = {0};
int tot = 0;

int win[MAXN*MAXN] = {0};
int lose[MAXN*MAXN] = {0};

struct node
{
    int num,sum;
}c[MAXN] = {0};

bool cmp(const node &a, const node &b){return (a.sum>b.sum);}
int main()
{
#ifndef ONLINE_JUDGE
    freopen("sgu138.in","r",stdin);
    freopen("sgu138.out","w",stdout);
#endif

    scanf("%d",&n);

    for(int i = 1 ; i <= n ; i++)
     {  scanf("%d",&cnt[i]); tot += cnt[i];}
    tot >>= 1;      

    for(int i = 1 ; i <= n ; i++)
     {
        c[i].num = i;
        c[i].sum = cnt[i];
     }

    std::sort(c + 1 , c + n + 1 , cmp);

    for(int i = 1 , j = 1; i <= tot ; i++)    
    {
        if(c[j].sum == 1)
        {
          lose[i] = c[j].num;
          c[j].sum --; j ++;
        }

        win[i] = c[j].num;
        c[j].sum --;
    }


    c[n+1].sum = -1;

    for (int i = 1 , j = 1; i <= tot; i++)
    {
        if (lose[i]) continue;

        while(!c[j].sum) j++;

        lose[i] = c[j].num;
        c[j].sum--;
    }
    printf("%d\n", tot);
    for (int i = 1; i <= tot; ++i)
        printf("%d %d\n", win[i], lose[i]);



#ifndef ONLINE_JUDGE        
    fclose(stdin);
    fclose(stdout);
#endif  
}