add 5.7.1.c

1 files changed, 110 insertions, 0 deletions

diff --git a/5.7.1.c b/5.7.1.c
new file mode 100644
index 0000000..dc7403b
--- /dev/null
+++ b/5.7.1.c
@@ -0,0 +1,110 @@
+#include <stdio.h>
+#include <string.h>
+
+#define MAXLINES 5000
+#define MAXLEN 1000
+char line[MAXLINES][MAXLEN]; /* same as `char (line[MAXLEN])[MAXLINES]` */
+/* we are using a lineptr here because array `line` pointer is const like all arrays and there addreses cant be changed to sort them only values can be exchanged
+ * but copying each char back and forth would take up more resources  and using a lineptr is much more efficent, here we are not actully sorting line itself
+ * but sorting pointers in lineptr to reflect the order*/
+char *lineptr[MAXLINES]; /* same as `char *(lineptr[MAXLINES])` */
+
+int readlines(char *lineptr[], int max);
+void writelines(char *lineptr[], int max);
+void my_qsort(char *lineptr[], int left, int right);
+
+int 
+main(void)
+{
+  int nlines;
+
+  if ((nlines = readlines(lineptr, MAXLINES)) > 0) {
+    my_qsort(lineptr, 0, nlines);
+    writelines(lineptr, nlines);
+    return 0;
+  } else {
+    printf("Err: lines, lines everywhere\n"); /* too much lines / input too big */
+    return 1;
+  }
+  return 0;
+}
+
+int sneed_getline(char str[], int max);
+
+int 
+readlines(char *lineptr[], int max)
+{
+  int len, nlines;
+
+  for (nlines = 0; (len = sneed_getline(line[nlines], MAXLEN)) > 0; nlines++) {
+    if (nlines < max) {
+      lineptr[nlines] = line[nlines];
+    } 
+    
+    else
+      return -1;
+  }
+
+  return nlines;
+}
+
+void 
+writelines(char *lineptr[], int max)
+{
+  while (max--)
+    printf("%s\n", *lineptr++);
+}
+
+int 
+sneed_getline(char str[], int max)
+{
+  char input;
+  char *str_og;
+
+  str_og = str;
+
+  --max;
+  while (--max && (input = getchar()) != EOF && input != '\n')
+    *str++ = input;
+
+  /*
+  if (input == '\n' && max)
+    *str++ = input; */ 
+
+  *str = '\0';
+
+  return str - str_og;
+}
+
+void swap(char *lineptr[], int to, int from);
+
+void 
+my_qsort(char *lineptr[], int left, int right)
+{
+  int i, last;
+
+  if (left >= right)
+    return;
+
+  swap (lineptr, left, (left+right)/2);
+
+  last = left;
+
+  for (i = left+1; i < right; i++)
+    if (strcmp(lineptr[i], lineptr[left]) < 0)
+      swap(lineptr, i, ++last);
+
+  swap(lineptr, left, last);
+  my_qsort(lineptr, left, last - 1);
+  my_qsort(lineptr, last + 1, right);
+}
+
+void 
+swap(char *lineptr[], int to, int from)
+{
+  char *temp;
+
+  temp = lineptr[to];
+  lineptr[to] = lineptr[from];
+  lineptr[from] = temp;
+}