#1199. 90岁的张哥哥

https://sjzezoj.com/submission/46232

S2OJ/1199/1199.cpp

@@ -1,34 +1,120 @@
-#pragma GCC optimize("Ofast")
-
-#include <algorithm>
 #include <iostream>
 #include <limits>
+#include <stack>
 
 using std::cin;
 using std::cout;
 using std::endl;
 
+// Limits
 const int N = 300005;
 
-int n, c, l, r, a[N];
+// Variables
+int a[N];
 bool vis[N];
 
+// Segment Tree
+void build(int, int, int);
+int query(int, int, int);
+
 int main() {
     std::ios::sync_with_stdio(false);
+
+    int n, c;
     cin >> n >> c;
     for (int i = 1; i <= n; i++) {
         cin >> a[i];
     }
-    l = 1, r = c;
-    for (int i = 1; i <= n; i++) {
-        int p = std::min_element(a + l, a + r + 1) - a;
-        cout << a[p] << ' ';
-        vis[p] = true;
-        a[p] = std::numeric_limits<int>::max();
-        while (p && vis[p]) p--;
-        l = std::max(p, 1);
-        r = std::min(r + 1, n);
+
+    a[0] = std::numeric_limits<int>::max();
+    build(1, 1, n);
+
+    int pos = query(1, 1, c);
+    std::stack<int> st;
+
+    for (int i = 1; i < pos; i++) {
+        st.push(i);
     }
+    cout << a[pos] << ' ';
+
+    for (int i = c + 1; i <= n; i++) {
+        int p = query(1, pos + 1, i);
+        if (!st.empty() && a[st.top()] <= a[p]) {
+            cout << a[st.top()] << ' ';
+            st.pop();
+        } else {
+            for (int j = pos + 1; j < p; j++) {
+                st.push(j);
+            }
+            pos = p;
+            cout << a[p] << ' ';
+        }
+    }
+
+    for (int i = 1; i < c; i++) {
+        int p = pos + 1 <= n ? query(1, pos + 1, n) : 0;
+        if (!st.empty() && a[st.top()] <= a[p]) {
+            cout << a[st.top()] << ' ';
+            st.pop();
+        } else {
+            for (int j = pos + 1; j < p; j++) {
+                st.push(j);
+            }
+            pos = p;
+            cout << a[p] << ' ';
+        }
+    }
+
     cout << endl;
+
     return 0;
 }
+
+// === Segment Tree ===
+
+struct node {
+    int l, r, id;
+
+    node()
+        : l(0), r(0), id(0) {}
+    node(int _l, int _r)
+        : l(_l), r(_r), id(0) {}
+} tr[N << 2];
+
+inline void pushup(int u) {
+    tr[u].id = a[tr[u << 1].id] <= a[tr[u << 1 | 1].id] ? tr[u << 1].id : tr[u << 1 | 1].id;
+}
+
+void build(int u, int l, int r) {
+    tr[u] = node(l, r);
+    if (l == r) {
+        tr[u].id = l;
+        return;
+    }
+    int mid = l + r >> 1;
+    build(u << 1, l, mid);
+    build(u << 1 | 1, mid + 1, r);
+    pushup(u);
+}
+
+/**
+ * 查询区间 [l, r] 最小值，并返回最小值在 a 数组中对应的**下标**
+ * @param u 根节点坐标
+ * @param l 区间左端点
+ * @param r 区间右端点
+ * @return 最小值在 a 数组中对应的**下标**
+ */
+int query(int u, int l, int r) {
+    if (l <= tr[u].l && tr[u].r <= r) return tr[u].id;
+    int mid = tr[u].l + tr[u].r >> 1,
+        pos = 0;
+    if (l <= mid) {
+        int t = query(u << 1, l, r);
+        if (a[t] < a[pos]) pos = t;
+    }
+    if (r > mid) {
+        int t = query(u << 1 | 1, l, r);
+        if (a[t] < a[pos]) pos = t;
+    }
+    return pos;
+}