C语言实现堆排序代码

C语言实现堆排序代码

void heapsort(int arr[], unsigned int N)  
{  
    unsigned int n = N, i = n/2, parent, child;  
    int t;  
  
    for (;;) { /* Loops until arr is sorted */  
        if (i > 0) { /* First stage - Sorting the heap */  
            i--;           /* Save its index to i */  
            t = arr[i];    /* Save parent value to t */  
        } else {     /* Second stage - Extracting elements in-place */  
            n--;           /* Make the new heap smaller */  
            if (n == 0) return; /* When the heap is empty, we are done */  
            t = arr[n];    /* Save last value (it will be overwritten) */  
            arr[n] = arr[0]; /* Save largest value at the end of arr */  
        }  
  
        parent = i; /* We will start pushing down t from parent */  
        child = i*2 + 1; /* parent's left child */  
  
        /* Sift operation - pushing the value of t down the heap */  
        while (child < n) {  
            if (child + 1 < n  &&  arr[child + 1] > arr[child]) {  
                child++; /* Choose the largest child */  
            }  
            if (arr[child] > t) { /* If any child is bigger than the parent */  
                arr[parent] = arr[child]; /* Move the largest child up */  
                parent = child; /* Move parent pointer to this child */  
                //child = parent*2-1; /* Find the next child */  
                child = parent*2+1; /* the previous line is wrong*/  
            } else {  
                break; /* t's place is found */  
            }  
        }  
        arr[parent] = t; /* We save t in the heap */  
    }  
}