From 1abb8b20bbdffbfa1f585df06a28e439c92ef9b4 Mon Sep 17 00:00:00 2001
From: zeroway <M_O_Bz@163.com>
Date: Tue, 19 Feb 2019 16:31:26 +0000
Subject: [PATCH] BugFix : loop out of range will cause stack smashing

    Data Sorted
    Shell Sort Big O Notation:
    --> Best Case: O(n log(n))
    --> Average Case: depends on gap sequence
    --> Worst Case: O(n)

    Time spent sorting: 0.000006
    *** stack smashing detected ***: <unknown> terminated
    Aborted
---
 sorting/shellSort.c | 98 +++++++++++++++++++++++++++------------------
 1 file changed, 59 insertions(+), 39 deletions(-)

diff --git a/sorting/shellSort.c b/sorting/shellSort.c
index e81cad95..ac392a90 100644
--- a/sorting/shellSort.c
+++ b/sorting/shellSort.c
@@ -2,47 +2,67 @@
 #include <stdlib.h>
 #include <time.h>
 
-void shellSort(int array[], int value){
-  int i = value;
-  int j, k, tmp;
-  for (i = value / 2; i > 0; i = i / 2){
-    for (j = i; j < value; j++){
-      for(k = j - i; k >= 0; k = k - i){
-        if (array[k+i] >= array[k]){
-          break;
-        }
-        else{
-          tmp = array[k];
-          array[k] = array[k+i];
-          array[k+i] = tmp;
-        }
-      }
-    }
-  }
+#define ELEMENT_NR 20
+#define ARRAY_LEN(x) (sizeof(x)/sizeof((x)[0]))
+const char *notation = "Shell Sort Big O Notation:\
+						\n--> Best Case: O(n log(n)) \
+						\n--> Average Case: depends on gap sequence \
+						\n--> Worst Case: O(n)";
+
+void show_data(int arr[], int len)
+{
+	int i;
+
+	for (i = 0; i < len; i++)
+		printf("%3d ", arr[i]);
+	printf("\n");
 }
 
+void swap(int *a, int *b)
+{
+	int tmp;
 
-int main(){
-
-    int array[20];
-    int range = 500;
-    for(int i = 0; i < 100; i++){
-     array[i] = rand() % range + 1;
-    }
-    int size = sizeof array / sizeof array[0];
-
-
-
-    clock_t start = clock();
-    shellSort(array,size);
-    clock_t end = clock();
-    double time_spent = (double)(end - start) / CLOCKS_PER_SEC;
-
-
-    printf("Data Sorted\n");
-    printf("%s\n", "Shell Sort Big O Notation:\n--> Best Case: O(n log(n))\n--> Average Case: depends on gap sequence\n--> Worst Case: O(n)\n");
-    printf("Time spent sorting: %f\n", time_spent);
-
-  return 0;
+	tmp = *a;
+	*a = *b;
+	*b = tmp;
 }
 
+void shellSort(int array[], int len)
+{
+	int i, j, gap;
+
+	for (gap = len / 2; gap > 0; gap = gap / 2)
+		for (i = gap; i < len; i++)
+			for (j = i - gap; j >= 0 && array[j] > array[j + gap]; j = j - gap)
+				swap(&array[j], &array[j + gap]);
+}
+
+int main(int argc, char *argv[])
+{
+	int i;
+	int array[ELEMENT_NR];
+	int range = 500;
+	int size;
+	clock_t start, end;
+	double time_spent;
+
+	srand(time(NULL));
+	for (i= 0; i < ELEMENT_NR; i++)
+		array[i] = rand() % range + 1;
+
+	size = ARRAY_LEN(array);
+
+	show_data(array, size);
+	start = clock();
+	shellSort(array, size);
+	end = clock();
+	time_spent = (double)(end - start) / CLOCKS_PER_SEC;
+
+	printf("Data Sorted\n");
+	show_data(array, size);
+
+	printf("%s\n", notation);
+	printf("Time spent sorting: %f\n", time_spent);
+
+	return 0;
+}