Tree Transversal

index.ts

interface TreeNode {
 left: TreeNode | null;
 right: TreeNode | null;
 val: number;
};
 
 
function main(node: TreeNode) {
   const list: string[] = [];
   transversal('', node);
   console.log(`The list is ${list}`);
   const result = list.reduce( (total: number, value: string) => {
   return total + Number(value);
   }, 0);
   console.log(`The result is ${result}`);
 
   function transversal(valList: string, node: TreeNode) {
     valList += node.val.toString();
     if(node.left != null) {
       transversal(valList, node.left);
     }
 
     if(node.right != null) {
       transversal(valList, node.right);
     }
 
     if(node.left == null && node.right == null) {
       list.push(valList);
     }
   }
}
 
const node: TreeNode = {
 left: {
   left: null,
   right: null,
   val: 17,
 },
 right: {
   left: null,
   right: null,
   val: 9,
 },
 val: 12,
};
 
main(node);