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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. // Speed
  5. #define fast_io ios::sync_with_stdio(0); cin.tie(0); cout.tie(0)
  6. // Typedefs
  7. #define int long long
  8. #define pb push_back
  9. #define ff first
  10. #define ss second
  11. #define all(x) (x).begin(), (x).end()
  12. #define sz(x) ((int)(x).size())
  13. #define endl '\n'
  14.  
  15. void solve() {
  16.     int n, m;
  17.     cin >> n >> m;
  18.     vector<pair<int, int>> a(n);
  19.     int sum_others = 0;
  20.  
  21.     for(int i = 0; i < n; i++) {
  22.         cin >> a[i].ff;
  23.         a[i].ss = i + 1; // Store original 1-based index
  24.     }
  25.  
  26.     // Sort elves by value (smallest to largest)
  27.     sort(all(a));
  28.  
  29.     // --- CASE 1: We want 0 survivors ---
  30.     if (m == 0) {
  31.         int king_idx = n - 1;
  32.         int king_hp = a[king_idx].ff;
  33.  
  34.         // Calculate damage potential from all others
  35.         int total_dmg = 0;
  36.         for(int i = 0; i < n - 1; i++) total_dmg += a[i].ff;
  37.  
  38.         if (total_dmg < king_hp) {
  39.             cout << -1 << endl;
  40.             return;
  41.         }
  42.  
  43.         vector<pair<int, int>> moves;
  44.         // Smallest elves attack the King until King dies
  45.         for(int i = 0; i < n - 1; i++) {
  46.             moves.pb({a[i].ss, a[king_idx].ss});
  47.             king_hp -= a[i].ff; // King takes damage
  48.             if (king_hp <= 0) break; // Stop if King is dead
  49.         }
  50.  
  51.         cout << sz(moves) << endl;
  52.         for(auto p : moves) cout << p.ff << " " << p.ss << endl;
  53.         return;
  54.     }
  55.  
  56.     // --- CASE 2: We want m survivors ---
  57.  
  58.     // We need m victims for m survivors to safely "attack" and lock themselves.
  59.     // Total needed: m (Survivors) + m (Victims) = 2m.
  60.     if (n < 2 * m) {
  61.         cout << -1 << endl;
  62.         return;
  63.     }
  64.  
  65.     // Groups logic (based on sorted array):
  66.     // Trash:     Indices 0 to (n - 2m - 1)
  67.     // Targets:   Indices (n - 2m) to (n - m - 1)
  68.     // Survivors: Indices (n - m) to (n - 1)
  69.  
  70.     vector<pair<int, int>> moves;
  71.  
  72.     // 1. Process Trash (Chain them to get rid of them)
  73.     // Trash 0 -> Trash 1 -> ... -> Trash Last -> Target 0
  74.     int trash_count = n - 2 * m;
  75.     int first_target_idx = n - 2 * m;
  76.  
  77.     if (trash_count > 0) {
  78.         for (int i = 0; i < trash_count; i++) {
  79.             if (i == trash_count - 1) {
  80.                 // Last trash attacks the first target
  81.                 moves.pb({a[i].ss, a[first_target_idx].ss});
  82.             } else {
  83.                 // Trash attacks next trash
  84.                 moves.pb({a[i].ss, a[i+1].ss});
  85.             }
  86.         }
  87.     }
  88.  
  89.     // 2. Survivors attack Targets
  90.     // We pair Survivor[i] with Target[i]
  91.     for (int i = 0; i < m; i++) {
  92.         int target_idx = n - 2 * m + i;
  93.         int survivor_idx = n - m + i;
  94.  
  95.         // Survivor attacks Target
  96.         moves.pb({a[survivor_idx].ss, a[target_idx].ss});
  97.     }
  98.  
  99.     // Output
  100.     cout << sz(moves) << endl;
  101.     for(auto p : moves) {
  102.         cout << p.ff << " " << p.ss << endl;
  103.     }
  104. }
  105.  
  106. int32_t main() {
  107.     fast_io;
  108.     int t;
  109.     cin >> t;
  110.     while(t--) {
  111.         solve();
  112.     }
  113.     return 0;
  114. }
Success #stdin #stdout 0s 5320KB
comments (?)
stdin
copy 
7
4 2
1 4 2 3
2 2
6 7
3 0
1 2 3
3 1
1 2 3
3 2
1 2 3
4 1
2 3 4 5
6 0
998244353 1000000000 314159265 676767677 999999999 987654321
stdout
copy 
2
4 1
2 3
-1
2
1 3
2 3
2
1 2
3 2
-1
3
1 2
2 3
4 3
3
3 2
4 2
6 2
https://ideone.com/wnVDkh
language:
C++ (gcc 8.3)
created:
13 days ago
visibility:
public

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