C++ practice

BST_struct.cpp

#include <iostream>
using namespace std;

struct node{
	int val;
	struct node *right, *left;
};

struct node *createNode(int item){
	struct node *temp = (struct node *)malloc(sizeof(struct node));
	temp->val = item;
	temp->right = NULL;
	temp->left = NULL;
	return temp;
}

struct node *insert(struct node *root, int n){
	if(root == NULL){
		root = createNode(n);
	}
	else if(root->val<n){
		root->right = insert(root->right, n);
	}
	else if(root->val>=n){
		root->left = insert(root->left, n);
	}
	
	return root;
}

void inorder(struct node *root){
	if(root != NULL){
		inorder(root->left);
		cout<<(*root).val<<" ";
		inorder(root->right);
	}
}

int main() {
	// your code goes here
	int arr[] = {23,1,45,67,89,9};
	int len = sizeof(arr)/sizeof(arr[0]);
	
	struct node *root = insert(root, arr[0]);;
	for(int i=1;i<len;i++){
		insert(root, arr[i]);
	}
	inorder(root);
	return 0;
}

char_count.cpp

#include <iostream>
#include <map>
#include <string>
// #include <cctype>
#include <iterator>
using namespace std;

char lower(char ip){
	if(ip>='A' && ip<='Z'){
		ip = ip - ('Z'-'z');
	}
	return ip;
}

int main() {
	// your code goes here
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	cout.tie(NULL);
	
	string str;
	cin>>str;
	
	for(int i=0;i<str.size();i++){
		str[i] = tolower(str[i]);
	}
	
	map<char, int> m;
	for(int i=0;i<str.length();i++){
		char key = str.at(i);
		map<char, int>::iterator found = m.find(key);
		if(found != m.end()){
			m[key] = m[key] + 1;
		}
		else{
			m.insert(make_pair(key, 1));
			// m[key] = 1;
		}
	}
	
	// map<char, int>::iterator itr;
	for(auto i=m.begin();i!=m.end();i++){
		cout<<i->first<<"  "<<i->second<<endl;
	}
	return 0;
}

dfs.cpp

#include <iostream>
#include <vector>
using namespace std;

void print_mat(vector<vector <int>> adj_mat){
	for(int i=0;i<adj_mat.size();i++){
		for(int j=0;j<adj_mat[i].size();j++){
			cout<<adj_mat[i][j]<<"  ";
		}
		cout<<endl;
	}
}

void dfs(vector<int> stack, vector<vector <int>> adj_mat, int visited[]){
	if(!stack.empty()){
		int t_root = stack.back();
		stack.pop_back();
		if(visited[t_root]==0){
			cout<<t_root<<endl;
			visited[t_root] = 1;
			
			for(int i=0;i<adj_mat[t_root].size();i++){
				stack.push_back(adj_mat[t_root][i]);
			}
			dfs(stack, adj_mat,visited);
		}
	}
}

void print_dfs(int root, vector<int> stack, vector<vector <int>> adj_mat, int n){
	stack.push_back(root);
	int visited[n];
	for(int i=0;i<n;i++){
		visited[i] = 0;
	}
	dfs(stack, adj_mat, visited);	
}

int main() {
	int n, ne, temp;
	cin>>n;
	vector<vector <int>> adj_mat;
	//adjacency matrix
	for(int i=0;i<n;i++){
		cin>>ne;
		vector<int> temp_vec;
		for(int j=0;j<ne;j++){
			cin>>temp;
			temp_vec.push_back(temp);
		}
		adj_mat.push_back(temp_vec);
	}
	
	int root;
	vector<int> stack;
	cin>>root;
	print_dfs(root, stack, adj_mat, n);
	// print_mat(adj_mat);
	
	return 0;
}

merge_linkedlist.cpp

#include <iostream>
#include <algorithm>
#include <climits>
using namespace std;

struct node{
	int val;
	struct node *next;
};

struct node *create_node(){
	struct node *root = (struct  node *)malloc(sizeof(struct node));
	root->val = INT_MIN;
	root->next = NULL;
	return root;
}

void print_array(int arr[], int n){
	for(int i=0;i<n;i++){
		cout<<arr[i]<<" ";
	}
	cout<<endl;
}

void print_ll(struct node *root){
	while(root!=NULL && root->val>INT_MIN){
		cout<<root->val<<" ";
		root = root->next;
	}
	cout<<endl;
}

int main() {
	// your code goes here
	int m,n;
	cin>>m>>n;
	int a1[m], a2[n];
	for(int i=0;i<m;i++){
		cin>>a1[i];
	}
	for(int i=0;i<n;i++){
		cin>>a2[i];
	}
	
	sort(a1,a1+m);
	sort(a2,a2+n);
	
	print_array(a1,m);
	print_array(a2,n);
	
	struct node *root = create_node();
	struct node *m_root = root;
	int k =0, l=0, j=0;
	int arr[m+n];
	while(k<m && l<n){
		if(a1[k]<a2[l]){
			arr[j] = a1[k];
			
			root->val = a1[k];
			root->next = create_node();
			root = root->next;
			
			k++;
		}
		else{
			arr[j] = a2[l];
			
			root->val = a2[l];
			root->next = create_node();
			root = root->next;
			
			l++;
		}
		j++;
	}
	while(k<m){
		arr[j] = a1[k];
		
		root->val = a1[k];
		root->next = create_node();
		root = root->next;
		
		k++;
		j++;
	}
	while(l<n){
		arr[j] = a2[l];
		
		root->val = a2[l];
		root->next = create_node();
		root = root->next;
		
		l++;
		j++;
	}
	
	print_array(arr,m+n);
	print_ll(m_root);
	return 0;
}