2016 Update

Task/Sorting-algorithms-Heapsort/C/sorting-algorithms-heapsort.c

@@ -1,58 +1,50 @@
 #include <stdio.h>
-#include <stdlib.h>
 
-#define ValType double
-#define IS_LESS(v1, v2)  (v1 < v2)
-
-void siftDown( ValType *a, int start, int count);
-
-#define SWAP(r,s)  do{ValType t=r; r=s; s=t; } while(0)
-
-void heapsort( ValType *a, int count)
-{
-    int start, end;
-
-    /* heapify */
-    for (start = (count-2)/2; start >=0; start--) {
-        siftDown( a, start, count);
+int max (int *a, int n, int i, int j, int k) {
+    int m = i;
+    if (j < n && a[j] > a[m]) {
+        m = j;
     }
+    if (k < n && a[k] > a[m]) {
+        m = k;
+    }
+    return m;
+}
 
-    for (end=count-1; end > 0; end--) {
-        SWAP(a[end],a[0]);
-        siftDown(a, 0, end);
+void downheap (int *a, int n, int i) {
+    while (1) {
+        int j = max(a, n, i, 2 * i + 1, 2 * i + 2);
+        if (j == i) {
+            break;
+        }
+        int t = a[i];
+        a[i] = a[j];
+        a[j] = t;
+        i = j;
     }
 }
 
-void siftDown( ValType *a, int start, int end)
-{
-    int root = start;
-
-    while ( root*2+1 < end ) {
-        int child = 2*root + 1;
-        if ((child + 1 < end) && IS_LESS(a[child],a[child+1])) {
-            child += 1;
-        }
-        if (IS_LESS(a[root], a[child])) {
-            SWAP( a[child], a[root] );
-            root = child;
-        }
-        else
-            return;
+void heapsort (int *a, int n) {
+    int i;
+    for (i = (n - 2) / 2; i >= 0; i--) {
+        downheap(a, n, i);
+    }
+    for (i = 0; i < n; i++) {
+        int t = a[n - i - 1];
+        a[n - i - 1] = a[0];
+        a[0] = t;
+        downheap(a, n - i - 1, 0);
     }
 }
 
-
-int main()
-{
-    int ix;
-    double valsToSort[] = {
-        1.4, 50.2, 5.11, -1.55, 301.521, 0.3301, 40.17,
-        -18.0, 88.1, 30.44, -37.2, 3012.0, 49.2};
-#define VSIZE (sizeof(valsToSort)/sizeof(valsToSort[0]))
-
-    heapsort(valsToSort, VSIZE);
-    printf("{");
-    for (ix=0; ix<VSIZE; ix++) printf(" %.3f ", valsToSort[ix]);
-    printf("}\n");
+int main () {
+    int a[] = {4, 65, 2, -31, 0, 99, 2, 83, 782, 1};
+    int n = sizeof a / sizeof a[0];
+    int i;
+    for (i = 0; i < n; i++)
+        printf("%d%s", a[i], i == n - 1 ? "\n" : " ");
+    heapsort(a, n);
+    for (i = 0; i < n; i++)
+        printf("%d%s", a[i], i == n - 1 ? "\n" : " ");
     return 0;
 }