Merge pull request #69 from SummerSad/master

Thanks for contributing

sorting/HeapSort.c

@@ -0,0 +1,70 @@
+// Heap sort
+#include <stdio.h>
+
+void printArr(int *A, int size)
+{
+    for (int i = 0; i < size; i++)
+    {
+        printf("%d ", A[i]);
+    }
+    printf("\n");
+}
+
+void swap(int *a, int *b)
+{
+    int temp = *a;
+    *a = *b;
+    *b = temp;
+}
+
+// heap looks like
+// 9 1 2 8 3 4 7 5
+//  9   8   4   7
+//     9       7
+//         9
+// the array is heap mean arr[i]>max(arr[i*2+1],arr[i*2+2])
+// the arr[0] is max of the array
+void heapShift(int *arr, int index, int size)
+{
+    // put arr[index] to arr[index+1..size-1] follow heap
+    int i = index;
+    int j = 2 * i + 1;
+    while (j < size)
+    {
+        if (j != size - 1) // there exist j and j+1
+        {
+            if (arr[j + 1] > arr[j]) // find max of arr[j] and arr[j+1]
+                j++;
+        }
+        if (arr[i] > arr[j]) // already heap
+            break;
+        swap(&arr[i], &arr[j]);
+        // move i, j
+        i = j;
+        j = i * 2 + 1;
+    }
+}
+
+void heapSort(int *arr, int size)
+{
+    // the array is split to to half
+    // just care the first half to put heap
+    for (int i = size / 2; i >= 0; i--)
+    {
+        heapShift(arr, i, size);
+    }
+    for (int i = size - 1; i >= 0; i--)
+    {
+        swap(&arr[0], &arr[i]); // move max of array to the end
+        heapShift(arr, 0, i);   // find max of arr[0..i-1], move to arr[0]
+    }
+}
+
+int main()
+{
+    int A[] = {9, 8, 7, 6, 5, 4, 3, 2, 1};
+    int size = sizeof(A) / sizeof(A[0]);
+    heapSort(A, size);
+    printArr(A, size);
+    return 0;
+}