自己猜测了一下  按比赛次数 从大到小排  然后类似于模拟 先排胜的场次 当只剩一场 将它定义为败

#include <cstdio>

#include <cstdlib>

#include <cmath>

#include <map>

#include <set>

#include <stack>

#include <vector>

#include <sstream>

#include <string>

#include <cstring>

#include <algorithm>

#include <iostream>

#define maxn 100010

#define INF 0x7fffffff

#define inf 10000000

#define MOD 1000000007

#define ull unsigned long long

#define ll long long

using namespace std;

struct node

{

    int id, x;

    bool operator < (const node& p) const

    {

        return x > p.x;

    }

};

node pp[110];

int win[maxn], lose[maxn];

void solve(int sum)

{

    int j = 0;

    for(int i =0 ; i < sum; ++ i)

    {

        while(!pp[j].x) j++;

        if(pp[j].x > 1)

        {

            win[i] = pp[j].id;

            pp[j].x--;

        }

        else if(pp[j].x == 1)

        {

            lose[i] = pp[j].id;

            pp[j].x--;

            j++;

            win[i] = pp[j].id;

            pp[j].x--;

        }

    }

    j = 0;

    for(int i =0 ; i < sum; ++ i)

    {

        if(lose[i]) continue;

        while(!pp[j].x) j++;

        if(pp[j].x > 1)

        {

            lose[i] = pp[j].id;

            pp[j].x--;

        }

        else if(pp[j].x == 1)

        {

            lose[i] = pp[j].id;

            pp[j].x--;

            j++;

        }

    }

}

int main()

{

    int n;

    while(scanf("%d", &n) == 1)

    {

        int sum = 0;

        for(int i = 0; i < n; ++ i)

        {

            scanf("%d", &pp[i].x);

            pp[i].id = i+1;

            sum += pp[i].x;

        }

        sort(pp, pp+n);

        memset(win, 0, sizeof(win));

        memset(lose, 0, sizeof(lose));

        sum /= 2;

        solve(sum);

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

        for(int i = 0; i < sum; ++ i)

            printf("%d %d\n", win[i], lose[i]);

    }

    return 0;

}