From 8e70de5278c2e0ec2a4fc7a7af322dabf88e4229 Mon Sep 17 00:00:00 2001
From: "Claudio Maggioni (maggicl)" <maggicl@kolabnow.ch>
Date: Fri, 26 Jul 2019 00:05:56 +0200
Subject: [PATCH] Done sort-lines exercise

---
 .gitignore            |  3 ++
 sortlines/sortlines.c | 98 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 101 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 sortlines/sortlines.c

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..6bc2222
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,3 @@
+sortlines/sortlines
+**/.ccls-cache
+**/.gdb_history
diff --git a/sortlines/sortlines.c b/sortlines/sortlines.c
new file mode 100644
index 0000000..e3655c6
--- /dev/null
+++ b/sortlines/sortlines.c
@@ -0,0 +1,98 @@
+// vim: set ts=4 sw=4 et tw=80:
+#include <stdio.h>
+#include <ctype.h>
+#include <unistd.h>
+#include <string.h>
+#include <stdbool.h>
+#define MAX_LINE_SIZE 1001
+#define DEBUG
+
+void swap(char** a, char** b);
+void print_words(char* words[], size_t start, size_t end);
+void quicksort_string(char* strings[static 1], size_t start, size_t end);
+
+void swap(char** a, char** b) {
+    char* tmp;
+    tmp = *a;
+    *a = *b;
+    *b = tmp;
+}
+
+void quicksort_string(char* strings[static 1], size_t start, size_t end) {
+
+#ifdef DEBUG
+    sleep(1);
+    printf("%ld - %ld: ", start, end);
+    print_words(strings, start, end);
+    putchar('\n');
+#endif
+
+    if (end - start <= 2) {
+#ifdef DEBUG
+        puts("returning");
+#endif
+        return;
+    }
+
+    char* pivot = strings[end - 1];
+    size_t i, gt = end - 1;
+    for (i = start; i < gt; i++) {
+#ifdef DEBUG
+        printf("i=%ld gt=%ld\n", i, gt);
+        print_words(strings, start, end);
+        putchar('\n');
+#endif
+        if (strcmp(strings[i], pivot) > 0) {
+            swap(&strings[--gt], &strings[i--]);
+        }
+    }
+    swap(&strings[gt], &strings[end - 1]);
+
+#ifdef DEBUG
+    print_words(strings, start, gt);
+    printf("| %s | ", strings[gt]);
+    print_words(strings, gt + 1, end);
+    putchar('\n');
+#endif
+
+    quicksort_string(strings, start, gt);
+    quicksort_string(strings, gt + 1, end);
+}
+
+void print_words(char* words[], size_t start, size_t end) {
+    size_t i;
+    for (i = start; i < end; i++) {
+        printf("%s ", words[i] == NULL ? "NULL" : words[i]);
+    }
+}
+
+int main() {
+    char line[MAX_LINE_SIZE];
+    char* words[MAX_LINE_SIZE / 2];
+    char* word = line;
+    size_t chars = 0, words_len = 0;
+    int c;
+    bool last_alpha = false;
+    while ((c = getchar()) != EOF) {
+        if (!isalpha(c) || c == '\n') {
+            if (last_alpha) {
+                line[chars++] = '\0';
+                words[words_len++] = word;
+                word = line + chars;
+                last_alpha = false;
+            }
+            if (c == '\n') {
+                quicksort_string(words, 0, words_len);
+                print_words(words, 0, words_len);
+                putchar('\n');
+                chars = 0;
+                words_len = 0;
+                word = line;
+            }
+        } else {
+            line[chars++] = c;
+            last_alpha = true;
+        }
+    }
+}
+