C - Looking for Order

https://codeforces.com/contest/8/submission/181040070

Codeforces/8/C/C.cpp

@@ -0,0 +1,67 @@
+#include <iostream>
+#include <cmath>
+#include <cstring>
+#include <utility>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 25;
+
+int n, f[1 << N], g[1 << N];
+std::pair<int, int> a[N];
+
+int dis(int u, int v) {
+    return std::pow(a[u].first - a[v].first, 2) + std::pow(a[u].second - a[v].second, 2);
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> a[0].first >> a[0].second >> n;
+
+    for (int i = 1; i <= n; i++) {
+        cin >> a[i].first >> a[i].second;
+    }
+
+    memset(f, 0x3f, sizeof(f));
+    f[0] = 0;
+
+    for (int s = 1; s < 1 << n; s++) {
+        int i = __builtin_ffs(s) - 1;
+
+        for (int t = s; t; t ^= (t & -t)) {
+            int j = __builtin_ffs(t) - 1;
+            int w = f[s ^ ((1 << i) | (1 << j))] + dis(0, i + 1) + dis(i + 1, j + 1) + dis(j + 1, 0);
+
+            if (w < f[s]) {
+                f[s] = w;
+                g[s] = s ^ ((1 << i) | (1 << j));
+            }
+        }
+    }
+
+    int s = (1 << n) - 1;
+
+    cout << f[s] << endl;
+
+    while (s) {
+        int t = s ^ g[s];
+        int a = __builtin_ffs(t & -t) - 1,
+            b = __builtin_ffs(t ^ (1 << a)) - 1;
+
+        if (~b) {
+            cout << 0 << ' ' << a + 1 << ' ' << b + 1 << ' ';
+        } else {
+            cout << 0 << ' ' << a + 1 << ' ';
+        }
+
+        s = g[s];
+    }
+
+    cout << 0 << endl;
+
+    return 0;
+}