1184. 欧拉回路

https://www.acwing.com/problem/content/submission/code_detail/14914342/

AcWing/1184/1184.cpp

@@ -0,0 +1,94 @@
+#include <iostream>
+#include <cstring>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 1e5 + 5,
+          M = 2e5 + 5;
+
+int t, n, m, cnt, ans[M];
+int idx, head[N], edge[M << 1], next[M << 1];
+int din[N], dout[N];
+bool vis[M << 1];
+
+void add(int u, int v) {
+    next[idx] = head[u];
+    edge[idx] = v;
+    head[u] = idx++;
+}
+
+void dfs(int u) {
+    for (int &i = head[u]; ~i;) {
+        if (vis[i]) {
+            i = next[i];
+            continue;
+        }
+
+        int v = edge[i];
+
+        vis[i] = true;
+        if (t == 1) vis[i ^ 1] = true;
+
+        int x;
+        if (t == 1) x = i & 1 ? -(i >> 1) - 1 : (i >> 1) + 1;
+        else x = i + 1;
+
+        i = next[i];
+
+        dfs(v);
+
+        ans[++cnt] = x;
+    }
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> t >> n >> m;
+
+    memset(head, 0xff, sizeof(head));
+
+    for (int i = 1, u, v; i <= m; i++) {
+        cin >> u >> v;
+
+        add(u, v);
+        if (t == 1) add(v, u);
+
+        din[u]++, dout[v]++;
+    }
+
+    for (int i = 1; i <= n; i++) {
+        if (t == 1 && (din[i] + dout[i] & 1) || t == 2 && (din[i] != dout[i])) {
+            cout << "NO" << endl;
+
+            exit(0);
+        }
+    }
+
+    for (int i = 1; i <= n; i++) {
+        if (~head[i]) {
+            dfs(i);
+
+            break;
+        }
+    }
+
+    if (cnt < m) {
+        cout << "NO" << endl;
+
+        exit(0);
+    }
+
+    cout << "YES" << endl;
+
+    for (int i = cnt; i; i--) {
+        cout << ans[i] << ' ';
+    }
+
+    cout << endl;
+
+    return 0;
+}