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min_stack.c
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min_stack.c
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#include <stdlib.h>
#include <stdio.h>
#include <limits.h>
#define PARENT(i) (i - 1) / 2
#define LEFT(i) 2 * i + 1
#define RIGHT(i) 2 * i + 2
typedef struct Heap {
int* a;
int heapsize;
} Heap;
void print_array(int* a, int size) {
for(int i = 0; i < size; i++) {
printf("%d ", a[i]);
}
printf("\n");
}
void exchange(int* a, int i, int j) {
int temp = a[i];
a[i] = a[j];
a[j] = temp;
}
void print_heap(Heap* h) {
printf("==\nArray: ");
print_array(h->a, h->heapsize);
printf("Heapsize: %d\n==\n", h->heapsize);
}
int peek(Heap* h) {
return h->a[0];
}
void heap_decrease_value(Heap* h, int i, int val) {
h->a[i] = val;
while(i > 0 && h->a[PARENT(i)] > h->a[i]) {
exchange(h->a, i, PARENT(i));
i = PARENT(i);
}
}
int min_heapify(Heap* h, int i) {
int l = LEFT(i);
int r = RIGHT(i);
int smallest = i;
if(l < h->heapsize && h->a[l] < h->a[i])
smallest = l;
if(r < h->heapsize && h->a[r] < h->a[smallest])
smallest = r;
if(smallest != i) {
exchange(h->a, i, smallest);
return min_heapify(h, smallest);
}
return i;
}
void min_insert(Heap* h, int val) {
h->heapsize++;
h->a[h->heapsize - 1] = INT_MAX;
heap_decrease_value(h, h->heapsize - 1, val);
}
int min_poll(Heap* h) {
int min = h->a[0];
h->a[0] = h->a[h->heapsize - 1];
h->heapsize--;
min_heapify(h, 0);
return min;
}
void min_remove(Heap* h, int x) {
int index = -1;
for(int i = 0; i < h->heapsize; i++) {
if(h->a[i] == x) {
index = i;
break;
}
}
if(index == -1) {
printf("Element doesnt exist\n");
return;
}
exchange(h->a, index, h->heapsize - 1);
h->heapsize--;
int i = min_heapify(h, 0);
printf("INDEX IS %d\n", i);
}
typedef struct {
int* stack;
Heap* heap;
int max_size;
int size;
} MinStack;
/** initialize your data structure here. */
MinStack* minStackCreate(int maxSize) {
MinStack* min_stack = (MinStack *) malloc(sizeof(MinStack));
min_stack->max_size = maxSize;
min_stack->size = 0;
min_stack->heap = (Heap *) malloc(sizeof(Heap));
min_stack->heap->a = (int *) malloc(maxSize * sizeof(int));
min_stack->heap->heapsize = 0;
min_stack->stack = (int *) malloc(maxSize * sizeof(int));
return min_stack;
}
void minStackPush(MinStack* obj, int x) {
obj->stack[obj->size++] = x;
min_insert(obj->heap, x);
}
void minStackPop(MinStack* obj) {
int remove = obj->stack[--obj->size];
min_remove(obj->heap, remove);
}
int minStackTop(MinStack* obj) {
return obj->stack[obj->size - 1];
}
int minStackGetMin(MinStack* obj) {
return peek(obj->heap);
}
void minStackFree(MinStack* obj) {
// TODO not needed for the problem
}
/**
* Your MinStack struct will be instantiated and called as such:
* struct MinStack* obj = minStackCreate(maxSize);
* minStackPush(obj, x);
* minStackPop(obj);
* int param_3 = minStackTop(obj);
* int param_4 = minStackGetMin(obj);
* minStackFree(obj);
*/