In my program, I pick a pivot p from a database S of strings, compute the median r of the distances of other string objects to p and then divide the other objects into roughly equal-sized subsets S1 and S2 as follows:

S1={o e S \{p}|d(p,o)<r}

S2={o e S \{p}|d(p,o)>=r}

where d(p,o) is the distance of the database object o to pivot p.Thus, the objects in S1 are inside the ball of radius r around p, while the objects in S2 are outside this ball. Applying this rule recursively leads to a binary tree,where a pivot object is stored in each internal node, with the left and right subtrees corresponding to the subsets inside and outside the corresponding ball,respectively.

Below I give the function for the above criteria but when I call the function from main and try to print the tree in preorder, nothing gets printed nor does the program terminate. I will really appreciate if someone can help me find the errors in my code and where I am going wrong:

Code:void query_ball() { string str; int i=0,p; int arr[1000]; char B[40]; char C[40]; vector<string> myStrings(1000); int r; int n1; ifstream file("text.txt"); //this file is the database containing 1000 strings for(p=0;p<1000;p++) { getline(file,str); strcpy(B,str.c_str()); myStrings[p]=B; // copying the file strings to vector myStrings } srand(time(0)); int pos; pos=rand()%1000; strcpy(C,myStrings[pos].c_str()); // C is the pivot picked randomly for(i=pos;i<=998;i++) // deleting element at myStrings[pos] which contains pivot C myStrings[i]=myStrings[i+1]; myStrings[i]=""; for(p=0;p<999;p++) { strcpy(B,myStrings[p].c_str()); arr[p]=edit(B,C); // arr contains edit distances between other string objects and pivot C } /*edit function relates to edit distances of pivot from other string objects. An edit distance between 2 strings is found by changing one string to another with the minimum number of insertions, deletions and/or replacement of characters in the strings.*/ n1=(999+1)/2; r=arr[n1]; // r is the median of the distances of other objects to pivot C for (p=-1; p<999; p++) //p starts with -1 to check first if Root is Null { if (Root == NULL) { Root = new TreeNode(); Root->val = C; } else { TreeNode* temp = Root; while(temp!=NULL) { strcpy(B,myStrings[p].c_str()); if (edit(B,C)<r) // checking distances inside ball of radius r { if (temp->LChild==NULL) { TreeNode* t = new TreeNode(); t->val = B; temp->LChild=t; } else { TreeNode* t = new TreeNode(); t->val = B; temp->LChild = temp->LChild->t; } } if (edit(B,C)>=r) // checking distances outside ball of radius r { if (temp->RChild==NULL) { TreeNode* t = new TreeNode(); t->val = B; temp->RChild=t; } else { TreeNode* t = new TreeNode(); t->val = B; temp->RChild = temp->RChild->t; } } } } } }