Why is malloc() return type causing and error?

[winterMute84]

I am writing a program to display the nodes of a graph in a depth-first traversal.

however I get these error messages
Error 1 error C2440: '=' : cannot convert from 'void *' to 'mynode *'

2 IntelliSense: a value of type "void *" cannot be assigned to an entity of type "mynode *"

I am using visual studio 2013, the errors come from this line

  	temp = malloc(sizeof(mynode));

and the full implementation is this

  	#include <stdio.h>
#include <iostream>
using namespace std;

typedef struct node {
	int value;
	struct node *right;
	struct node *left;
} mynode;

mynode *root;

void add_node(int value);

void levelOrderTraversal(mynode *root);

int main(int argc, char* argv[]) {
	root = NULL;

	add_node(5);
	add_node(1);
	add_node(-20);
	add_node(100);
	add_node(23);
	add_node(67);
	add_node(13);

	printf("\n\n\nLEVEL ORDER TRAVERSAL\n\n");
	levelOrderTraversal(root);

	system("pause");
	return 0;
}

// Function to add a new node...
void add_node(int value) {
	mynode *prev, *cur, *temp;

	temp = malloc(sizeof(mynode));
	temp->value = value;
	temp->right = NULL;
	temp->left = NULL;

	if (root == NULL) {
		printf("\nCreating the root..\n");
		root = temp;
		return;
	}

	prev = NULL;
	cur = root;

	while (cur != NULL) {
		prev = cur;
		//cur = (value < cur->value) ? cur->left:cur->right;
		if (value < cur->value) {
			cur = cur->left;
		}
		else {
			cur = cur->right;
		}
	}

	if (value < prev->value) {
		prev->left = temp;
	}
	else {
		prev->right = temp;
	}
}

// Level order traversal..
void levelOrderTraversal(mynode *root) {
	mynode *queue[100] = { (mynode *)0 }; // Important to initialize!
	int size = 0;
	int queue_pointer = 0;

	while (root) {
		printf("[%d] ", root->value);
		if (root->left) {
			queue[size++] = root->left;
		}

		if (root->right) {
			queue[size++] = root->right;
		}
		root = queue[queue_pointer++];
	}
}

[Chervil]

If you write in C++, put

    temp = static_cast<mynode *> ( malloc(sizeof(mynode)) );

or use new and delete instead of malloc() / free().

    temp = new mynode;

If you write in C, put

    temp = (mynode *)  malloc(sizeof(mynode)) ;

and remember to include the header <stdlib.h>

[AbstractionAnon]

First off, are you writing C or C++?

Line 1: This is a C header, not a C++ header.

Line 28,45,79: If you're writing C++, you should be using cout, not printf.

Line 39: Why are you using malloc (assuming you're writing C++). malloc is a C library function. For C++, you should be doing:

  temp = new mynode;

If you're writing C, then you need to cast malloc's return value.

  temp = (mynode *) malloc (sizeof(mynode));