Merge pull request #293 from tanshen-kun/tanshen-kun

Added Naive Pattern Searching Algorithm in C

Author: Pradeepsingh61

C/algorithms/string_algorithms/naive_pattern.c

@@ -0,0 +1,110 @@
+/*
+ * Algorithm: Naive String Matching
+ * Description: Simple pattern matching algorithm that checks for the pattern
+ *              at every position in the text without any preprocessing.
+ * Time Complexity: O(n * m) in worst case (n = text length, m = pattern length)
+ * Space Complexity: O(1)
+ * Author: tanshen-kun
+ *
+ * Hacktoberfest2025
+ */
+
+#include <stdio.h>
+#include <string.h>
+
+/**
+ * Naive string matching algorithm
+ * Searches for all occurrences of a pattern in a given text
+ *
+ * @param text : string / text to search
+ * @param pattern : pattern to search
+ * @return : None
+ */
+void naive_search(char *text, char *pattern) {
+  int textLength = strlen(text);
+  int patternLength = strlen(pattern);
+  int occurrences = 0;
+
+  if (patternLength == 0 || patternLength > textLength) {
+    printf("[x] No occurrences found.\n");
+    return;
+  }
+
+  printf("[-] Searching for pattern %s in text %s:\n", pattern, text);
+
+  for (int i = 0; i <= textLength - patternLength; i++) {
+    int j;
+    for (j = 0; j < patternLength; j++) {
+      if (text[i + j] != pattern[j]) {
+        break;
+      }
+    }
+
+    if (j == patternLength) {
+      printf("[*] Pattern found at index %d\n", i);
+      occurrences++;
+    }
+  }
+
+  if (occurrences == 0) {
+    printf("[x] Pattern not found in text.\n");
+  } else {
+    printf("[*]Total occurrences: %d\n", occurrences);
+  }
+}
+
+/**
+ * Test function with multiple test cases
+ */
+void test_naive_algorithm() {
+
+  // Test case 1: Simple match
+  printf("[-] Test Case 1 - Simple Pattern Matching:\n");
+  char text1[] = "ABAAABCDABABCABCABCDAB";
+  char pattern1[] = "ABCAB";
+  naive_search(text1, pattern1);
+  printf("\n");
+
+  // Test case 2: Multiple occurrences
+  printf("[-] Test Case 2 - Multiple Occurrences:\n");
+  char text2[] = "ABABCABABA";
+  char pattern2[] = "ABA";
+  naive_search(text2, pattern2);
+  printf("\n");
+
+  // Test case 3: Pattern not found
+  printf("[-] Test Case 3 - Pattern Not Found:\n");
+  char text3[] = "ABCDEFGHIJK";
+  char pattern3[] = "XYZ";
+  naive_search(text3, pattern3);
+  printf("\n");
+
+  // Test case 4: Pattern at beginning
+  printf("[-] Test Case 4 - Pattern at Beginning:\n");
+  char text4[] = "HELLO WORLD";
+  char pattern4[] = "HELLO";
+  naive_search(text4, pattern4);
+  printf("\n");
+
+  // Test case 5: Pattern at end
+  printf("[-] Test Case 5 - Pattern at End:\n");
+  char text5[] = "PROGRAMMING";
+  char pattern5[] = "ING";
+  naive_search(text5, pattern5);
+  printf("\n");
+}
+
+int main() {
+  printf("[--- Naive String Matching Algorithm in C ---]\n\n");
+
+  test_naive_algorithm();
+
+  printf("Algorithm Information :\n");
+  printf("=> Time Complexity: O(n * m)\n");
+  printf("=> Space Complexity: O(1)\n");
+  printf("=> No preprocessing or optimization\n");
+  printf("=> Useful for small strings\n");
+  printf("=> Inefficient for large inputs or repetitive patterns\n");
+
+  return 0;
+}