diff --git a/bst.cpp b/bst.cpp
new file mode 100644
index 0000000..494b72c
--- /dev/null
+++ b/bst.cpp
@@ -0,0 +1,119 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+class BST
+{
+public:
+    BST()
+    {
+        root = NULL;
+    }
+
+    struct node
+    {
+        int data;
+        node *l;
+        node *r;
+        node(int a)
+        {
+            data = a;
+            l = r = NULL;
+        }
+    };
+
+    node *root;
+
+    void insert(int a)
+    {
+        node *temp = new node(a);
+        node *prev = root;
+        if (root == NULL)
+            root = temp;
+        else
+        {
+            while (1)
+            {
+                if (prev->data > a)
+                {
+                    if (prev->l == NULL)
+                    {
+                        prev->l = temp;
+                        break;
+                    }
+                    else
+                        prev = prev->l;
+                }
+                else
+                {
+                    if (prev->r == NULL)
+                    {
+                        prev->r = temp;
+                        break;
+                    }
+                    else
+                        prev = prev->r;
+                }
+            }
+        }
+    }
+
+    void del(int a)
+    {
+        node *temp = root;
+        node **prev = &root;
+        while (temp->data != a)
+        {
+            if (temp->data < a)
+                prev = &(temp->r), temp = temp->r;
+            else
+                prev = &(temp->l), temp = temp->l;
+        }
+        node *rep = NULL;
+
+        if (temp->r == NULL)
+        {
+            if (temp->l == NULL)
+                *prev = NULL;
+            else
+            {
+                rep = temp->l;
+                while (rep->r != NULL)
+                    rep = rep->r;
+                int rd = rep->data;
+                del(rep->data);
+                (*prev)->data = rd;
+            }
+        }
+        else
+        {
+            rep = temp->r;
+            while (rep->l != NULL)
+                rep = rep->l;
+            int rd = rep->data;
+            del(rep->data);
+            (*prev)->data = rd;
+        }
+    }
+
+    void inorder(node *root)
+    {
+        if (root == NULL)
+            return;
+        inorder(root->l);
+        cout << root->data << " ";
+            inorder(root->r);
+    }
+};
+
+
+int main(){
+    BST bst;
+    bst.insert(29);
+    bst.insert(30);
+    bst.insert(1);
+    bst.insert(-15);
+    bst.insert(99);
+    bst.insert(1025);
+    bst.inorder(bst.root);
+    bst.del(1);
+}
\ No newline at end of file
diff --git a/topological_sort.cpp b/topological_sort.cpp
new file mode 100755
index 0000000..6ea2a40
--- /dev/null
+++ b/topological_sort.cpp
@@ -0,0 +1,85 @@
+#include <bits/stdc++.h>
+#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL)
+#define endl '\n'
+#define int long long int
+using namespace std;
+#define pii pair <int, int>
+#define mii map<int, int>
+#define pb push_back
+#define deb(x) cout << #x << " " << x << endl;
+#define deb2(x, y) cout << #x << " " << x << " " << #y << " " << y << endl;
+#define pt(a) cout << a << endl;
+#define ptt(a, b) cout << a << " " << b << endl;
+#define ptf(a) cout << a << " ";
+#define rd(a) cin >> a;
+#define rdd(a, b) cin >> a >> b;
+#define loop(s, e, itr) for (int itr = s; itr < e; itr++)
+#define lop(n) for(int i = 0; i < n; i++)
+#define lopj(n) for(int j = 0; j < n; j++)
+#define lopk(n) for(int k = 0; k < n; k++)
+#define vin vector<int>
+#define w(flag) int tc = 1; if(flag) cin >> tc; for(int t = 1; t <= tc; t++)
+#define vec vector
+#define mod 1000000007
+#define all(x) x.begin(), x.end()
+#define elif else if
+#define nline cout << endl;
+
+
+int ar[1000006] = {0};
+int n = 0, m;
+int tp(0), tp1(0), tp2(0), tp3(0), tp4(0);
+string str;
+int len;
+void pre_processing(){}
+
+vin adj[100005];
+int vis[100005];
+
+stack<int> stk;
+
+void dfs(int node)
+{
+    vis[node] = true;
+    for(auto i : adj[node])
+        if(!vis[i])
+            dfs(i);
+
+    stk.push(node);
+}
+
+void solve()
+{
+    cin >> n >> m;
+    lop(m)
+    {
+        rdd(tp, tp1)
+        adj[tp].pb(tp1);
+    }
+    memset(vis, 0, sizeof(vis));
+    loop(1, n+1, i)
+        if(!vis[i])
+            dfs(i);
+    
+    vin sorted_nodes;
+    while(!stk.empty())
+    {
+        sorted_nodes.push_back(stk.top());
+        stk.pop();
+    }
+    for(auto i : sorted_nodes)
+        cout << i << " ";
+    cout << endl;
+}
+
+int32_t main()
+{
+    fastio;
+    pre_processing();
+    w(0)
+    {
+        // cout << "Case #" << t << ": ";
+        solve();
+    }
+    return 0;
+}
\ No newline at end of file
diff --git a/trie.cpp b/trie.cpp
new file mode 100644
index 0000000..d91cb8a
--- /dev/null
+++ b/trie.cpp
@@ -0,0 +1,75 @@
+#include<bits/stdc++.h>
+using namespace std;
+
+class Trie
+{
+public:
+    struct node
+    {
+        node *child[26];
+        int count;
+        node()
+        {
+            for (int i = 0; i < 26; i++)
+                child[i] = NULL;
+            count = 0;
+        }
+    };
+
+    node *head;
+    Trie()
+    {
+        node *temp = new node();
+        head = temp;
+    }
+
+    void insert(string str)
+    {
+        int len = str.length();
+        node *temp = head;
+        for (int i = 0; i < len; i++)
+        {
+            int p = str[i] - 'a';
+            if (temp->child[p] == NULL)
+            {
+                node *n = new node();
+                temp->child[p] = n;
+            }
+            temp = temp->child[p];
+        }
+        temp->count++;
+    }
+
+    int count(node *hd)
+    {
+        int ans = 0;
+        if (hd->count != 0)
+            ans++; // to count distinct strings
+        //ans += hd->count;       // uncomment this line to count total strings (and comment just above line)
+        for (int i = 0; i < 26; i++)
+        {
+            if (hd->child[i] != NULL)
+            {
+                ans += count(hd->child[i]);
+            }
+        }
+        return ans;
+    }
+};
+
+int main(){
+    Trie trie;
+    trie.insert("arpit");
+    trie.insert("arpitgupta");
+    trie.insert("arpit");
+    trie.insert("arpitgupta");
+    trie.insert("arpitcodingtrie");
+    trie.insert("arpitgpta");
+    trie.insert("arpitgpta");
+    trie.insert("arpitgupta");
+    trie.insert("arpitgpta");
+    trie.insert("arpitcodingtrie");
+    trie.insert("arpitgpta");
+    trie.insert("arpitcodingtrie");
+    trie.count(trie.head);
+}
\ No newline at end of file