Question

function which returns the value which occurs most frequently in a linked list. if several values are equally most frequent the value that occurs earliest in the list is returned.

int most_frequent(struct node *head) {

// code here

}

Answer 1

//C program

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

struct node{
   int data;
   struct node*next;
};

struct node* addNode(struct node*list,int data){
   struct node*newnode = (struct node*)malloc(sizeof(struct node));
   newnode->data = data;
   newnode->next=NULL;
  
   if(!list)return newnode;
  
   struct node*current = list;
   while(current->next)current=current->next;
  
   current->next = newnode;
   return list;
}

void print(struct node*list){
   while(list){
       printf("%d ",list->data);
       list=list->next;
   }
   printf("\n\n");
}
int most_frequent(struct node *head) {
int i;
struct node*current = head;
int max = INT_MIN;
while(current){
    if(current->data>max)max = current->data;
    current = current->next;
}
int arr[max+1];

for( i=0;i<=max;i++)arr[i]=0;
current = head;

while(current){
    arr[current->data]++;
    current = current->next;
}
int maxCount = INT_MIN;
for( i=0;i<=max;i++){
    if(arr[i]>maxCount)maxCount=arr[i];
}
current = head;

while(current){
    if(arr[current->data]==maxCount)return current->data;
    current = current->next;
}

}

int main(){
   struct node* head = NULL;
   head = addNode(head,3);
   head = addNode(head,3);
   head = addNode(head,2);
   head = addNode(head,3);
   head = addNode(head,2);
   head = addNode(head,2);
  
   printf("current list \n");
   print(head);
  
   printf("\n\nMost Frequent element : %d\n",most_frequent(head));
  
   return 0;
}

//sample output