Create LIS On Tree.cpp

Author: MathProgrammer

Contests/AtCoder Beginner Contest 165/Programs/LIS On Tree.cpp

@@ -0,0 +1,106 @@
+#include <iostream>
+#include <vector>
+#include <stack>
+
+using namespace std;
+
+const int MAX_N = 2e5 + 5;
+
+vector <stack <int> > minimum_ending_of_length(MAX_N);
+vector <int> A(MAX_N);
+vector <vector <int> > tree(MAX_N);
+vector <int> LIS_here(MAX_N);
+
+int find_first_greater(int n)
+{
+    int left = 0, right = MAX_N - 1;
+
+    //L < x <= R
+    while(right - left > 1)
+    {
+        int mid = (left + right)/2;
+
+        if(minimum_ending_of_length[mid].size() == 0 || minimum_ending_of_length[mid].top() >= n)
+        {
+            right = mid;
+        }
+        else
+        {
+            left = mid;
+        }
+    }
+
+    return right;
+}
+
+int find_LIS()
+{
+    int left = 0, right = MAX_N - 1;
+
+    //L <= x < R
+    while(right - left > 1)
+    {
+        int mid = (left + right)/2;
+
+        if(minimum_ending_of_length[mid].size() > 0)
+        {
+            left = mid;
+        }
+        else
+        {
+            right = mid;
+        }
+    }
+
+    return left;
+}
+
+void dfs(int v, int parent_v)
+{
+    int best_position = find_first_greater(A[v]);
+    minimum_ending_of_length[best_position].push(A[v]);
+
+    LIS_here[v] = find_LIS();
+
+    for(int child_v : tree[v])
+    {
+        if(child_v == parent_v)
+        {
+            continue;
+        }
+
+        dfs(child_v, v);
+    }
+
+    minimum_ending_of_length[best_position].pop();
+}
+
+int main()
+{
+    int no_of_vertices;
+    cin >> no_of_vertices;
+
+    for(int i = 1; i <= no_of_vertices; i++)
+    {
+        cin >> A[i];
+    }
+
+    int no_of_edges = no_of_vertices - 1;
+    for(int i = 1; i <= no_of_edges; i++)
+    {
+        int u, v;
+        cin >> u >> v;
+
+        tree[u].push_back(v);
+        tree[v].push_back(u);
+    }
+
+    dfs(1, 0);
+
+    for(int v = 1; v <= no_of_vertices; v++)
+    {
+        cout << LIS_here[v] << "\n";
+    }
+
+    return 0;
+}