rohith2506

// Using deque
void max_slid_window(vector<int> v){
  deque<int> q;
  for(int i=0; i<k; i++){
    while(!q.empty() && v[i] >= v[q.back()])
      q.pop_back();
    q.push_back(i);
  }
  
  for(int i=k+1; i<n; i++){

rohith2506

// Use parititon method of quick sort 

void quick_sort(vector<int> v){
  int i=-1;
  for(int j=0; j<n; j++){
    if(a[j] < 0){
      i++;
      swap(a[i],a[j]);
    }
  }

rohith2506

// diameter of binary tree
// consider a root --> diameter of a tree = max(if path goes through that root, if path does not go through that root)
// so diamter = max(lh+rh+1, max(ld,rd));

int diameter(node *t){
  if(t != NULL){
    int lh = height(t -> left);
    int rh = height(t -> right);
    
    int ld = diameter(t -> left);

rohith2506

// Converting bst to sorted DLL
// go in in order and and keep track of previous node and make it previous to current node and current node next to this node.
void bsttodll(node *root, node **head){
  if(root == NULL) return ;
  static node *prev = NULL;
  bsttodll(root->left, head);
  if(prev == NULL) *head = root;
  else {
    root -> previous = prev;
    prev -> next = previous;

rohith2506

// http://www.geeksforgeeks.org/next-greater-element/
// simple stack logic.

int nge(int a[]){
  vector<int> nge;
  stack<int> stk;
  stk.push(a[0]);
  for(int i=1; i<n; i++){
    int next = a[i];
    while( !stk.empty()){

rohith2506

/*
It's a modification of merge sort
see for explanation:- http://www.geeksforgeeks.org/counting-inversions/
*/
int merge_sort(int a[], int low, int high){
  if(high > low){
    int mid = (low + high)/2;
    inv_count  = merge_sort(a, low, mid);
    inv_count += merge_sort(a, mid+1, high);
    return merge(a, temp, low, mid, high);

rohith2506

// As though it looks like O(n^3) but it actally is O(n^2). because of k initialized outisde and does not depenv on j value.

int possible_triangles(vector<int> a){
  int count = 0;
  for(int i=0; i<n-2; i++){
    int k = i+2;
    for(int j=i+1; j<n; j++){
      while(k < n && a[i] + a[j] > a[k]) ++k;
      count = count + (k-j-1);
    }

rohith2506

http://ideone.com/eF7Nih

rohith2506

//http://www.geeksforgeeks.org/pancake-sorting/

void flip(vector<int> v, int i){
  int temp, start = 0;
  while(start < i){
    int temp = v[start];
    v[start] = v[i];
    v[i] = temp;
    start++;
    i--;

rohith2506

// Very good problem. But difficult to understand.
// http://leetcode.com/2010/11/finding-minimum-window-in-s-which.html

int search(vector<string> txt, vector<string> pat, string s1, string s2){
    for(int i=0; i<s2.length(); i++) pat[(int)(s2[i])]++;
    txt[256] = {0};
    int begin = 0, end = 0;
    while(end < s1.length()){
      if(pat[s1[end]] == 0) continue;
      txt[s1[end]]++l;