Add Boyer Moore search algo and simple Makefile

searching/pattern_search/Makefile

@@ -0,0 +1,14 @@
+CC = gcc
+FLAG = -o
+
+all: naive_search  rabin_karp_search boyer_moore_search
+
+naive_search      : naive_search.c
+	$(CC) $(FLAG) naive_search naive_search.c
+rabin_karp_search : rabin_karp_search
+	$(CC) $(FLAG) rabin_karp_search rabin_karp_search.c
+boyer_moore_search: boyer_moore_search boyer_moore_search.c
+	$(CC) $(FLAG) boyer_moore_search boyer_moore_search.c
+
+clean:
+	rm naive_search rabin_karp_search boyer_moore_search

searching/pattern_search/boyer_moore_search.c

@@ -0,0 +1,57 @@
+#include <stdio.h>
+#include <string.h>
+
+#define NUM_OF_CHARS 256
+
+int max(int a, int b) {return (a>b)? a:b;}
+
+void computeArray(char *pattern, int size, int arr[NUM_OF_CHARS])
+{
+    int i;
+
+    for(i = 0; i < NUM_OF_CHARS; i++)
+        arr[i] = -1;
+    /* Fill the actual value of last occurrence of a character */
+    for(i = 0; i < size; i++)
+        arr[(int) pattern[i]] = i;
+}
+/* Boyer Moore Search algorithm  */
+void boyer_moore_search(char *str, char *pattern)
+{
+    int n = strlen(str);
+    int m = strlen(pattern);
+    int shift = 0;
+    int arr[NUM_OF_CHARS];
+
+    computeArray(pattern, m, arr);
+    while(shift <= (n - m))
+    {
+        int j = m - 1;
+        while (j >= 0 && pattern[j] == str[shift + j])
+            j--;
+        if (j < 0)
+        {
+            printf("--Pattern is found at: %d\n", shift);
+            shift += (shift + m < n) ? m - arr[str[shift + m]] : 1;
+        } else {
+            shift += max(1, j - arr[str[shift +j]]);
+        }
+    }
+}
+
+int main()
+{
+    char str[] = "AABCAB12AFAABCABFFEGABCAB";
+    char pat1[] = "ABCAB";
+    char pat2[] = "FFF"; /* not found */
+    char pat3[] = "CAB";
+
+    printf("String test: %s\n", str);
+    printf("Test1: search pattern %s\n", pat1);
+    boyer_moore_search(str, pat1);
+    printf("Test2: search pattern %s\n", pat2);
+    boyer_moore_search(str, pat2);
+    printf("Test3: search pattern %s\n", pat3);
+    boyer_moore_search(str, pat3);
+    return 0;
+}