backup

src/bin/cf-1884d.cc

@@ -296,30 +296,39 @@ void prep() {}
 
 void solve() {
     read(ll, n);
-    readvec(int, a, n);
-    unordered_counter(a, ct);
-    unordered_map<int, ll, safe_hash> dp;
-    set<int, greater<>> st(a.begin(), a.end());
+    vector<int> ct(n + 1);
+    vector<bool> has(n + 1);
+    for (int i = 0; i < n; ++i) {
+        read(int, x);
+        ct[x] += 1;
+    }
+    for (int x = 1; x <= n; ++x) {
+        if (!ct[x]) continue;
+        for (ll y = x; y <= n; y += x) {
+            has[y] = 1;
+        }
+    }
+    vector<ll> dp(n + 1);
     ll res = 0;
-    for (auto&& x : st) {
+    // enumerate gcd(a[i], a[j]) =: x
+    for (int x = n; x; --x) {
+        if (!has[x]) continue;
+        // cerr << x << ' ';
         ll curr = 0;
         for (ll y = x; y <= n; y += x) {
-            if (ct.count(y)) {
-                curr += ct[y];
-            }
+            curr += ct[y];
         }
         curr = curr * (curr - 1) / 2;
         for (ll y = x; y <= n; y += x) {
-            if (dp.count(y)) {
-                curr -= dp[y];
-            }
+            curr -= dp[y];
         }
         dp[x] = curr;
         res += curr;
     }
-    for (auto&& [x, y] : dp) {
-        cerr << "dp[" << x << "] = " << y << endl;
-    }
+    // cerr << endl;
+    // for (auto&& [x, y] : dp) {
+    //     cerr << "dp[" << x << "] = " << y << endl;
+    // }
     cout << n * (n - 1) / 2 - res << '\n';
 }
 

src/bin/test.py

@@ -1,6 +1,19 @@
-from random import randint
-print(100000)
-for _ in range(2):
-    for i in range(100000):
-        print(randint(0, 1), end='')
-    print()
+from typing import DefaultDict
+
+
+n = int(input())
+a = [int(x) for x in input().strip().split(' ')]
+d = sorted(list(set(a)), reverse=True)
+a.sort()
+slot = DefaultDict(lambda: [])
+slot_cnt = DefaultDict(lambda: 0)
+for i in range(n):
+    for j in range(i + 1, n):
+        for k in d:
+            if a[i] % k == 0 and a[j] % k == 0:
+                slot[k].append((a[i], a[j]))
+                slot_cnt[k] += 1
+                break
+
+print(slot)
+print(n * (n - 1) // 2 - sum(v for v in slot_cnt.values()))