Level Order (ZigZag)

Author: akashmodak97

Hacker Blocks/Level Order (ZigZag).cpp

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+/* Hacker Blocks */
+/* Title - Level Order (ZigZag) */
+/* Created By - Akash Modak */
+/* Date - 19/09/2020 */
+
+// Given a binary tree. Print the zig zag order i.e print level 1 from left to right, level 2 from right to left and so on. This means odd levels should get printed from left to right and even levels should be printed from right to left.
+
+// Input Format
+// Enter the values of all the nodes in the binary tree in pre-order format where true suggest the node exists and false suggests it is NULL
+
+// Constraints
+// None
+
+// Output Format
+// Display the values in zigzag level order in which each value is separated by a space
+
+// Sample Input
+// 10 true 20 true 40 false false true 50 false false true 30 true 60 false false true 73 false false
+// Sample Output
+// 10 30 20 40 50 60 73 
+
+#include<bits/stdc++.h>
+using namespace std;
+class node{
+	public:
+	int data;
+	node *left,*right;
+	node(int d){
+		data = d;
+		left=right=NULL;
+	}
+};
+node* build(string s){
+	if(s=="true"){
+		int d;
+		cin>>d;
+		node *root = new node(d);
+		string l;
+		cin>>l;
+		if(l=="true")
+		root->left = build(l);
+		string r;
+		cin>>r;
+		if(r=="true")
+		root->right = build(r);
+		return root;		
+	}
+	return NULL;
+}
+void zigzag(node* root){
+	queue<node*> q;
+	q.push(root);
+	bool flag = true;
+	while(!q.empty()){
+		vector<int> v;
+		int s = q.size();
+		while(s--){
+			node *temp = q.front();
+			q.pop();
+			v.push_back(temp->data);
+			if(temp->left)
+			q.push(temp->left);
+			if(temp->right)
+			q.push(temp->right);
+		}
+		if(!flag)
+		reverse(v.begin(),v.end());
+		for(auto x: v)
+		cout<<x<<" ";
+		flag= !flag;
+	}
+}
+int main() {
+	node* root=build("true");
+	zigzag(root);
+	return 0;
+}