Some Useful Data structure interview questions

Remove the leave Node

struct Node * romoveLeafList(struct Node * root){
    if(root==NULL) return NULL;
    if(root->left==NULL && root->right==NULL){
        return NULL;
    }
    root->left=romoveLeafList(root->left);
    root->right=romoveLeafList(root->right);
    return root;
 
}

Remove all the Node which has sum is less than k 

struct Node * sumofnode(struct Node *root, int k, int *sum)
{
    if(root==NULL)return NULL;
    int leftsum=*sum+root->data;
    int rightsum=leftsum;
    root->left=sumofnode(root->left,k,&leftsum);
    root->right=sumofnode(root->right,k,&rightsum);
    *sum=leftsum>rightsum?leftsum:rightsum;
    if(*sum<k)
    return NULL;
    return root;
}

Sub String Program

Given two String, s1 and s2. 
to find the longest substring which is prefix of s1, as well as suffix of s2. 
Complexity O(n)


#include <stdio.h>
#include <string.h>

main()
{
  char str1[]="abcdeee";
  char str2[]="sssssabc";
  int i=0,j,k,l;
  int n=strlen(str2);
  if(strlen(str1)<strlen(str2)){
      n=strlen(str1);
  }
  k=0;
  l=0;
  for(i=0;i<n;i++){
      j=strlen(str2)-n+i;
      if(str1[l++]!=str2[j]){
        i=k;
        k++;
        l=0;
      }
    }
    printf("%s",str2+strlen(str2)-n+k);

}

program to find the square root of a given number without using library function

    #include<stdio.h>

    float SquareRoot(float num);
    void main()
    {
    float input, ans;

  
    ans = SquareRoot(9);
    printf("\n Square Root : %f", ans);
  
    }
    float SquareRoot(float num)
    {
    if(num >= 0)
    {
    float x = num;
    int i;
    for(i = 0; i < 20; i ++)
    {
        x = (((x * x) + num) / (2 * x));
    }
    return x;
    }
    }

Given an array , find the nth largest and nth smallest number. Sorting should not be used

This is for 6 number you can make it as you want

void main(){

int a[]={8,4,6,7,4,1},i,l=0,s=0,count=1,flag=0,largest,smallest,ps,pl;

for(i=0;i<6;i++){

    if(a[l]<a[i]){

        if(flag){

            if(a[pl]>a[i])

            l=i;

        }

        else{

        l=i;

        }

    }

    if(a[s]>a[i]){

        if(flag){

            if(a[ps]<a[i])

            s=i;

        }

        else{

        s=i;

        }

    }

    if(i==5){

        count--;

        if(flag==0){

            smallest=s;

            largest=l;

            

        }

        if(count==0){

            break;

        }

        else{

            flag=1;

            pl=l;

            ps=s;

            l=smallest;

            s=largest;

            i=-1;

        }

       

    }

}

        

    

printf("small=%d big=%d",a[s],a[l]);

}

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