Nguyễn Quốc Khánh Nguyễn Quốc Khánh - 1 month ago 12
C Question

Heap Sort C doesn't work when change from array to array unsigned int

My code works properly when all variables and array are defined as int, but if I change the type to unsigned int, it won't work.

Here is my code:

#include <stdio.h>
#include <stdlib.h>
void swap(unsigned int *a, unsigned int *b){
unsigned int temp;
temp=*a ; *a=*b ; *b=temp;
}
void heapify(unsigned int A[], unsigned int i, unsigned int n){
//sort from root i

unsigned int L = 2*i+1;
// node left child
unsigned int R = 2*i+2;
//node right child
unsigned int max = i;
//set max node is root
if(L < n && A[L] > A[max]) max = L;
//if node child > max, set that node is max
if(R < n && A[R] > A[max]) max = R;
if(max != i) {
swap(&A[i], &A[max]);
heapify(A, max, n);//recursive tree with root is node swaped
}

}

void buildHeap(unsigned int A[], unsigned int n){

unsigned int i = n/2 - 1;
for(; i >= 0; i--) heapify(A, i, n);
}

void heapSort(unsigned int A[], unsigned int n){

buildHeap(A, n);
unsigned int i = n-1;
for(; i >= 0; i--){
swap(&A[0], &A[i]);
heapify(A, 0, i);
}
}

void PrintArray(unsigned int A[], unsigned int n){
unsigned int i;
for(i = 0; i < n; i++){
printf("%d ", A[i]);
}
}
int main(){
unsigned int A[]={1,6,8,9,7,1,65,92,2,9,2,5,73,9,1,5};
unsigned int n=sizeof (A)/sizeof(unsigned int);
PrintArray(A,n);
heapSort(A,n);
PrintArray(A,n);
}


The output is stuck at print the old array and nothing happens after that.

What should I do?

Answer

The problem is at buildHeap - you set your iterator as unsigned int, and run a loop until i is no longer positive - which in the cash of unsigned int will never happen.

void buildHeap(unsigned int A[], unsigned int n){

    unsigned int i = n/2 - 1;
    for(; i >= 0; i--) heapify(A, i, n);
    }
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