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Adding min heap

This commit is contained in:
Kaustav Bhattacharya 2019-09-25 20:54:12 +05:30
parent b23cbb387d
commit 8bec476f2c
1 changed files with 121 additions and 0 deletions
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data_structures/heap/minheap.c Normal file
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#include<stdio.h>
#include<stdlib.h>
typedef struct min_heap{
int *p;
int size;
int count;
}Heap;
Heap* create_heap(Heap* heap); /*Creates a min_heap structure and returns a pointer to the struct*/
void down_heapify(Heap* heap, int index);/*Pushes an element downwards in the heap to find its correct position*/
void up_heapify(Heap* heap, int index);/*Pushes an element upwards in the heap to find its correct position*/
void push(Heap* heap, int x);/*Inserts an element in the heap*/
void pop(Heap* heap);/*Removes the top element from the heap*/
int top(Heap* heap);/*Returns the top element of the heap or returns INT_MIN if heap is empty*/
int empty(Heap* heap);/*Checks if heap is empty*/
int size(Heap* heap);/*Returns the size of heap*/
int main(){
Heap* head = create_heap(head);
push(head, 10);
printf("Pushing element : 10\n");
push(head, 3);
printf("Pushing element : 3\n");
push(head, 2);
printf("Pushing element : 2\n");
push(head, 8);
printf("Pushing element : 8\n");
printf("Top element = %d \n", top(head));
push(head, 1);
printf("Pushing element : 1\n");
push(head, 7);
printf("Pushing element : 7\n");
printf("Top element = %d \n", top(head));
pop(head);
printf("Popping an element.\n");
printf("Top element = %d \n", top(head));
pop(head);
printf("Popping an element.\n");
printf("Top element = %d \n", top(head));
printf("\n");
return 0;
}
Heap* create_heap(Heap* heap){
heap = (Heap *)malloc(sizeof(Heap));
heap->size = 1;
heap->p = (int *)malloc(heap->size*sizeof(int));
heap->count = 0;
}
void down_heapify(Heap* heap, int index){
if(index>=heap->count)return;
int left = index*2+1;
int right = index*2+2;
int leftflag = 0, rightflag = 0;
int minimum = *((heap->p)+index);
if(left<heap->count && minimum>*((heap->p)+left)){
minimum = *((heap->p)+left);
leftflag = 1;
}
if(right<heap->count && minimum>*((heap->p)+right)){
minimum = *((heap->p)+right);
leftflag = 0;
rightflag = 1;
}
if(leftflag){
*((heap->p)+left) = *((heap->p)+index);
*((heap->p)+index) = minimum;
down_heapify(heap, left);
}
if(rightflag){
*((heap->p)+right) = *((heap->p)+index);
*((heap->p)+index) = minimum;
down_heapify(heap, right);
}
}
void up_heapify(Heap* heap, int index){
int parent = (index-1)/2;
if(parent<0)return;
if(*((heap->p)+index)<*((heap->p)+parent)){
int temp = *((heap->p)+index);
*((heap->p)+index) = *((heap->p)+parent);
*((heap->p)+parent) = temp;
up_heapify(heap, parent);
}
}
void push(Heap* heap, int x){
if(heap->count>=heap->size)return;
*((heap->p)+heap->count) = x;
heap->count++;
if(4*heap->count >= 3*heap->size){
heap->size *= 2;
(heap->p) = (int *)realloc((heap->p), (heap->size)*sizeof(int));
}
up_heapify(heap, heap->count - 1);
}
void pop(Heap* heap){
if(heap->count==0)return;
heap->count--;
int temp = *((heap->p)+heap->count);
*((heap->p)+heap->count) = *(heap->p);
*(heap->p) = temp;
down_heapify(heap, 0);
if(4*heap->count<=heap->size){
heap->size /= 2;
(heap->p) = (int *)realloc((heap->p), (heap->size)*sizeof(int));
}
}
int top(Heap* heap){
if(heap->count!=0)return *(heap->p);
else return INT_MIN;
}
int empty(Heap* heap){
if(heap->count!=0)return 0;
else return 1;
}
int size(Heap* heap){
return heap->count;
}