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DIV3 744 D.cpp
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#include <bits/stdc++.h>
using namespace std;
//#include <ext/pb_ds/assoc_container.hpp>
//#include <ext/pb_ds/tree_policy.hpp>
//using namespace __gnu_pbds;
//
//template<typename T> using pbds = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update> ;
typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
#define f(i,a,b) for(ll i=a;i<b;i++)
#define rev(i,a,b) for(ll i=a;i>=b;i--)
#define pb push_back
#define bp pop_back
#define mp make_pair
#define all(v) (v).begin() , (v).end()
#define ff first
#define ss second
#define sd(x) ((ll)(v).size())
#define print(x) cout<<x<<"\n"
#define itr(it, v) for (auto it = v.begin(); it != v.end(); it++)
#define PI 3.141592653589793238462
#define MOD 1000000007
#define MOD1 998244353
#define INF 1e13
#define inf 0x3f3f3f3f //1061109567
#define sp(x, y) fixed << setprecision(y) << x << endl;
#define pll pair<ll,ll>
#define zrobits(x) __builtin_ctzll(x)
#define setbits(x) __builtin_popcountll(x)
#define mem(x,y) memset(x, y, sizeof(x))
#define FAST_IO ios::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#ifndef ONLINE_JUDGE
#define debug(x) cerr << #x <<" "; PRINT(x); cerr << endl;
#else
#define debug(x)
#endif
void PRINT(ll t) {cerr << t;}
void PRINT(int t) {cerr << t;}
void PRINT(string t) {cerr << t;}
void PRINT(char t) {cerr << t;}
void PRINT(ld t) {cerr << t;}
void PRINT(double t) {cerr << t;}
void PRINT(ull t) {cerr << t;}
template <class T, class V> void PRINT(pair <T, V> p);
template <class T> void PRINT(vector <T> v);
template <class T> void PRINT(set <T> v);
template <class T, class V> void PRINT(map <T, V> v);
template <class T, class V> void PRINT(unordered_map <T, V> v);
template <class T> void PRINT(multiset <T> v);
template <class T, class V> void PRINT(pair <T, V> p) {cerr << "{"; PRINT(p.ff); cerr << ","; PRINT(p.ss); cerr << "}";}
template <class T> void PRINT(vector <T> v) {cerr << "[ "; for (T i : v) {PRINT(i); cerr << " ";} cerr << "]";}
template <class T> void PRINT(set <T> v) {cerr << "[ "; for (T i : v) {PRINT(i); cerr << " ";} cerr << "]";}
template <class T> void PRINT(multiset <T> v) {cerr << "[ "; for (T i : v) {PRINT(i); cerr << " ";} cerr << "]";}
template <class T, class V> void PRINT(map <T, V> v) {cerr << "[ "; for (auto i : v) {PRINT(i); cerr << " ";} cerr << "]";}
template <class T, class V> void PRINT(unordered_map <T, V> v) {cerr << "[ "; for (auto i : v) {PRINT(i); cerr << " ";} cerr << "]";}
ll power(ll x, ll y, ll mod) { ll res = 1; x = x % mod; while (y > 0) { if (y & 1) { res = (res * x);} y = y >> 1; x = (x * x); res = res % mod; x = x % mod;} return res % mod;}
ll invert(ll a, ll b) {return power(a, b - 2, b);} //For finding (a^-1)%b which equals to (a^(b-2) )%b(FERMAT'S LITTLE THEOREM)
ll combination(ll n, ll r, ll m, ll *fact, ll *ifact) {ll val1 = fact[n]; ll val2 = ifact[n - r]; ll val3 = ifact[r]; return (((val1 * val2) % m) * val3) % m;}
vector<ll> sieve(ll n) {ll*arr = new ll[n + 1](); vector<ll> vect; for (ll i = 2; i <= n; i++)if (arr[i] == 0) {vect.push_back(i); for (ll j = (ll(i) * ll(i)); j <= n; j += i)arr[j] = 1;} return vect;}
ll next_prime(ll n) {vector<ll>v = sieve(n + 400); auto it = upper_bound(all(v), n); return *it;} // Maximum difference between 2 prime numbers in range of 1 to 1e8 is 220
ll mod_add(ll a, ll b, ll m) {a = a % m; b = b % m; return (((a + b) % m) + m) % m;}
ll mod_mul(ll a, ll b, ll m) {a = a % m; b = b % m; return (((a * b) % m) + m) % m;}
ll mod_sub(ll a, ll b, ll m) {a = a % m; b = b % m; return (((a - b) % m) + m) % m;}
ll mod_div(ll a, ll b, ll m) {a = a % m; b = b % m; return (mod_mul(a, invert(b, m), m) + m) % m;} //If m is prime
ll gcd(ll x, ll y) { return y ? gcd(y, x % y) : x;}
ll lcm(ll x, ll y) {return (x * y) / gcd(x, y);}
inline long long MAX2(long long a, long long b) {return (a) > (b) ? (a) : (b);}
inline long long MAX3(long long a, long long b, long long c) {return (a) > (b) ? ((a) > (c) ? (a) : (c)) : ((b) > (c) ? (b) : (c));}
inline long long MIN2(long long a, long long b) {return (a) < (b) ? (a) : (b);}
inline long long MIN3(long long a, long long b, long long c) {return (a) < (b) ? ((a) < (c) ? (a) : (c)) : ((b) < (c) ? (b) : (c));}
// ll *fact = new ll[200000 + 5];
// ll *ifact = new ll[200000 + 5];
void solution()
{
ll n, x, y;
cin >> n;
vector<pair<ll, ll>>v;
priority_queue<pair<ll, ll>>pq;
f(i, 0, n) {cin >> x; if (x != 0)pq.push(mp(x, i + 1));}
ll a, b;
while (!pq.empty()) {
x = pq.top().ff;
y = pq.top().ss;
pq.pop();
if (pq.empty()) break;
a = pq.top().ff;
b = pq.top().ss;
pq.pop();
x--, a--; v.pb(mp(b, y));
if (a > 0) pq.push(mp(a, b));
if (x > 0) pq.push(mp(x, y));
}
cout << v.size() << endl;
for (auto i : v) {
cout << i.ff << " " << i.ss << endl;
}
}
signed main()
{
#ifndef ONLINE_JUDGE
freopen("check.txt", "w", stderr);
#endif
FAST_IO;
// // FOR FINDING FACTORIAL OF NUMBERS FROM 1 TO 2*10^5 and here MODULO is 1e9+7
// fact[0] = 1, ifact[0] = 1;
// for (ll i = 1; i <= 2e5; i++) {
// fact[i] = mod_mul(fact[i - 1], i, MOD);
// ifact[i] = invert(fact[i], MOD);
// }
ll t = 1;
cin >> t;
f(i, 0, t)
{
solution();
}
}