Merge Sort Tree

merge_sort_tree.cpp

@@ -0,0 +1,56 @@
+struct merge_sort_tree
+{
+    vector<vector<int>> tree;
+    vector<int> a;
+    merge_sort_tree(int n)
+    {
+        int sz = 1;
+        while(sz < n) sz <<= 1;
+        sz <<= 1;
+        tree.resize(sz);
+        a.resize(n);
+    }
+
+    void init(int ns, int ne, int node)//0, n-1, 1
+    {
+        if (ns == ne)
+        {
+            tree[node].resize(1);
+            tree[node][0] = a[ns];
+            return;
+        }
+        int mid = (ns + ne) / 2;
+        init(ns, mid, node * 2);
+        init(mid + 1, ne, node * 2 + 1);
+        tree[node].resize(tree[node * 2].size() + tree[node * 2 + 1].size());
+        merge(tree[node * 2].begin(), tree[node * 2].end(), tree[node * 2 + 1].begin(), tree[node * 2 + 1].end(),
+              tree[node].begin());
+    }
+    int qry_ub(int ns, int ne, int node, int qs, int qe, int val)//val 이하의 수가 몇개?
+    {
+        if (qs > ne || ns > qe) return 0;
+        if (qs <= ns && ne <= qe)
+        {
+            int m = upper_bound(tree[node].begin(), tree[node].end(), val) - tree[node].begin();
+            return m;
+        }
+        int mid = (ns + ne) / 2;
+        int t1 = qry_ub(ns, mid, node * 2, qs, qe, val);
+        int t2 = qry_ub(mid + 1, ne, node * 2 + 1, qs, qe, val);
+        return t1 + t2;
+    }
+
+    int qry_lb(int ns, int ne, int node, int qs, int qe, int val)//val 미만의 수가 몇개?
+    {
+        if (qs > ne || ns > qe) return 0;
+        if (qs <= ns && ne <= qe)
+        {
+            int m = lower_bound(tree[node].begin(), tree[node].end(), val) - tree[node].begin();
+            return m;
+        }
+        int mid = (ns + ne) / 2;
+        int t1 = qry_lb(ns, mid, node * 2, qs, qe, val);
+        int t2 = qry_lb(mid + 1, ne, node * 2 + 1, qs, qe, val);
+        return t1 + t2;
+    }
+};