'commit'

TangDou/AcWing/EulerPath/POJ1392.cpp

@@ -0,0 +1,59 @@
+#include <iostream>
+#include <algorithm>
+#include <queue>
+#include <map>
+#include <cstring>
+#include <vector>
+#include <stack>
+#include <cstdio>
+
+using namespace std;
+const int N = 1 << 16, M = N;
+int len;
+int rl, res[N];
+int st[N];
+
+// 链式前向星
+int e[M], h[N], idx, w[M], ne[M];
+void add(int a, int b, int c = 0) {
+    e[idx] = b, ne[idx] = h[a], w[idx] = c, h[a] = idx++;
+}
+
+void dfs(int u) {
+    for (int i = h[u]; ~i; i = h[u]) {
+        int id = w[i];
+        if (st[id]) continue;
+        st[id] = 1;
+        h[u] = ne[i]; // 删边的套路优化
+        dfs(e[i]);
+        res[rl++] = id;
+    }
+}
+
+int main() {
+#ifndef ONLINE_JUDGE
+    freopen("POJ1392.in", "r", stdin);
+#endif
+    int n, k;
+    while (scanf("%d%d", &n, &k), n + k) {
+        idx = rl = 0;
+        memset(h, -1, sizeof h);
+        memset(st, 0, sizeof st);
+        memset(res, 0, sizeof res);
+
+        len = 1 << (n - 1);
+        for (int a = 0; a < len; a++) {
+            int c = a << 1 | 1;
+            int b = c % len;
+            add(a, b, c);
+
+            c = a << 1;
+            b = c % len;
+            add(a, b, c);
+        }
+        dfs(0);
+        // 输出这个序列生成的第K个数字是多少？
+        printf("%d\n", res[rl - 1 - k]);
+    }
+    return 0;
+}