116.c

#include<stdio.h>
#include<stdlib.h>

structTreeLinkNode {
intval;
structTreeLinkNode*left, *right, *next;
};

voidconnectHelper(structTreeLinkNode*node, structTreeLinkNode*sibling) {
if (node==NULL) return;
if (!node->left|| !node->right) return;

/* node have two children */
node->left->next=node->right;
node->right->next= (sibling==NULL) ? NULL : sibling->left;

connectHelper(node->left, node->right);
connectHelper(node->right, node->right->next);
}

voidconnect(structTreeLinkNode*root) {
if (root==NULL) return;

root->next=NULL;
connectHelper(root, NULL);
}

intmain() {
structTreeLinkNode*root= (structTreeLinkNode*)calloc(7, sizeof(structTreeLinkNode));
root->val=1;
root->left=root+1;
root->left->val=2;
root->right=root+2;
root->right->val=3;

root->left->left=root+3;
root->left->left->val=4;
root->left->right=root+4;
root->left->right->val=5;

root->right->left=root+5;
root->right->left->val=6;
root->right->right=root+6;
root->right->right->val=7;

connect(root);

return0;
}