new file: 21.cpp

21.cpp

@@ -0,0 +1,52 @@
+// 106
+#include <bits/stdc++.h>
+using namespace std;
+int n;
+int a[100005], ord[100005], pos[100005];
+int pre[100005], nxt[100005];
+int ans[100005];
+int t;
+int main()
+{
+    scanf("%d", &t);
+    while (t--)
+    {
+        int ll;
+        scanf("%d %d", &ll, &n);
+        printf("%d %d\n", ll, (n + 1) >> 1);
+        for (int i = 1; i <= n; ++i)
+            scanf("%d", &a[i]), ord[i] = i;
+        sort(ord + 1, ord + n + 1, [](int x, int y)
+             { return a[x] != a[y] ? a[x] < a[y] : x < y; });
+        for (int rank = 1; rank <= n; ++rank)
+        {
+            int x = ord[rank];
+            pos[x] = rank, pre[x] = (rank == 1 ? 0 : ord[rank - 1]), nxt[x] = (rank == n ? 0 : ord[rank + 1]);
+        }
+        int mid = ord[n / 2 + 1], cnt = 0;
+        for (int len = n; len >= 1; --len)
+        {
+            if (len & 1)
+                ans[++cnt] = a[mid];
+            if (len == 1)
+                break;
+            int x = len;
+            if (len & 1)
+            {
+                if (pos[x] <= pos[mid])
+                    mid = nxt[mid];
+            }
+            else if (pos[x] >= pos[mid])
+                mid = pre[mid];
+            if (pre[x])
+                nxt[pre[x]] = nxt[x];
+            if (nxt[x])
+                pre[nxt[x]] = pre[x];
+        }
+        for (int i = cnt; i >= 1; --i)
+            printf("%d%c", ans[i], ((cnt - i + 1) % 10) ? ' ' : '\n');
+        if (cnt % 10)
+            puts("");
+    }
+    return 0;
+}