old stuff: algorithms

1 files changed, 116 insertions, 0 deletions

diff --git a/algorithms/bigrams.c b/algorithms/bigrams.c
new file mode 100644
index 0000000..ca40f49
--- /dev/null
+++ b/algorithms/bigrams.c
@@ -0,0 +1,116 @@
+#include <stdio.h>
+
+#define OUTPUT_WIDTH 72
+
+#define LARGE_ARRSZ 500
+#define SMALL_ARRSZ 5
+
+
+struct bigram {
+  char trail, lead;
+};
+
+int
+get_bigrams(char *text, struct bigram *bigrams, int max_bigrams)
+{
+	char *trail=text, *lead=text+1;
+	int i=0;
+	
+	while(*trail && *lead && (i<max_bigrams)) {
+		if (LARGE_ARRSZ<i) {
+			return -1;
+		}
+		bigrams[i].trail = *trail++;
+		bigrams[i].lead = *lead++;
+		i++;
+	}
+	
+	return i;
+}
+
+void
+print_bigrams(struct bigram *bigrams, int num_bigrams, int line_width)
+{
+	int i, retval=0;
+	
+	for(i = 0; i < num_bigrams; i += 1) {
+		retval += (printf("%c%c/", bigrams->trail, bigrams->lead));
+		if (retval > line_width) {
+			printf("\n");
+			retval=0;
+		}
+		*bigrams++;
+	}
+	printf("\n");
+}
+
+void
+test1(char *my_text)
+{
+	struct bigram largeArr[LARGE_ARRSZ];
+	int num_bigrams;
+
+	if ((num_bigrams = get_bigrams(my_text, largeArr, LARGE_ARRSZ))<LARGE_ARRSZ) {
+		printf("%d bigrams:\n", num_bigrams);
+		print_bigrams(largeArr, num_bigrams, OUTPUT_WIDTH);
+	}
+}
+
+void
+test2(char *my_text)
+{
+	struct bigram smallArr[SMALL_ARRSZ+1];
+	int num_bigrams;
+
+	smallArr[SMALL_ARRSZ].lead = '@';  /* sentinel for overwrites */
+	if ((num_bigrams = get_bigrams(my_text, smallArr, SMALL_ARRSZ))<SMALL_ARRSZ) {
+		printf("wrong bigram count!\n");
+	}
+	if (smallArr[SMALL_ARRSZ].lead!='@') {
+		printf("buffer overflow :-(\n");
+	}
+}
+
+int
+do_something(char *text, struct bigram *bigrams, int max)
+{
+  char *trail=text, *lead=text+1;
+  int i=0;
+
+  while(*trail && *lead && (i < max)) {
+    bigrams[i].trail = *trail++;
+    bigrams[i].lead = *lead++;
+    i++;
+  }
+
+  for(unsigned int j = 0; j < max; j += 1) {
+    printf("%c%c/\n", bigrams[j].trail, bigrams[j].lead);
+  }
+
+  printf("%d\n", i);
+
+  return i;
+}
+
+int main(void)
+{
+  struct bigram b = {'a', 'b'};
+  struct bigram b1 = {'b', 'c'};
+  struct bigram bigrams[3];
+  *bigrams = b;
+  *(bigrams+1) = b1;
+  for(unsigned int i = 0; i < 2; i += 1) {
+    printf("%c%c\n", bigrams[i].trail, bigrams[i].lead);
+  }
+
+  struct bigram bigrams1[3];
+  char *text = "abcd";
+  int max=3;
+  do_something(text, bigrams1, max);
+
+	char *my_text = "Ein Gespenst geht um in Europa";
+	test1(my_text);
+	test2(my_text);
+
+  return 0;
+}