Merge pull request #1435 from pratheekv39/feature/reverse_factor_algo…

…rithm

#1398 Added Reverse Factor Algorithm

String Algorithms/Reverse Factor Algorithm/Program.c

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+#include <stdio.h>
+#include <string.h>
+
+// Function to reverse a string
+void reverseString(char* str) {
+    int n = strlen(str);
+    for (int i = 0; i < n / 2; i++) {
+        char temp = str[i];
+        str[i] = str[n - i - 1];
+        str[n - i - 1] = temp;
+    }
+}
+
+// Function to check if a substring is a factor of the main string
+int isFactor(char* sub, char* str) {
+    int subLen = strlen(sub);
+    int strLen = strlen(str);
+
+    for (int i = 0; i <= strLen - subLen; i++) {
+        int j;
+        for (j = 0; j < subLen; j++) {
+            if (str[i + j] != sub[j])
+                break;
+        }
+        if (j == subLen)
+            return i;  // Substring found at index i
+    }
+
+    return -1; // Substring not found
+}
+
+// Function to implement the Reverse Factor Algorithm
+void reverseFactor(char* pattern, char* text) {
+    // Reverse the pattern
+    reverseString(pattern);
+
+    // Check if the reversed pattern is a factor of the text
+    int index = isFactor(pattern, text);
+
+    if (index != -1)
+        printf("Reversed pattern found at index %d\n", index);
+    else
+        printf("Reversed pattern not found\n");
+}
+
+int main() {
+    char text[] = "ABCDABCDABC";
+    char pattern[] = "ABC";
+
+    printf("Text: %s\n", text);
+    printf("Pattern: %s\n", pattern);
+
+    reverseFactor(pattern, text);
+
+    return 0;
+}

String Algorithms/Reverse Factor Algorithm/README.md

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+# Reverse Factor Algorithm
+
+## Description
+
+The Reverse Factor Algorithm is a string-searching algorithm that checks if the reverse of a given pattern appears as a substring within a text. It can be applied in various situations where reverse-pattern matching is required, such as palindrome detection or specific text searching.
+
+### Problem Definition
+
+Given:
+- A text string `T` of length `n`
+- A pattern string `P` of length `m`
+
+Objective:
+- Find if the reverse of pattern `P` is present in text `T` and report its position.
+
+### Algorithm Overview
+
+1. **Reverse the Pattern**: Reverse the characters of the pattern string `P`.
+2. **Search for the Reversed Pattern**: 
+   - Slide the reversed pattern over the text one character at a time.
+   - For each window of length `m` in the text, compare it with the reversed pattern.
+3. **Report Matches**: If the reversed pattern matches a substring in the text, report the starting index.
+
+### Key Features
+
+- Simple string comparison to check for reversed pattern matches
+- Applicable for reverse pattern detection in text or similar tasks
+- Time complexity is linear with respect to the length of the text for most cases
+
+### Time Complexity
+
+- Best and Average Case: O(n)
+- Worst Case: O(n * m), occurs when there are many partial matches in the text.
+
+### Space Complexity
+
+O(m), where `m` is the length of the pattern, as we store a reversed copy of the pattern.
+
+## Implementation
+
+The C implementation of the Reverse Factor Algorithm involves:
+
+1. A function to reverse the given pattern string.
+2. A function to check if the reversed pattern is a substring of the text.
+3. A main function that demonstrates the usage of the algorithm.
+
+## Usage
+
+Compile the program and run it. The example in the `main` function shows how the Reverse Factor Algorithm works by finding if the reverse of a given pattern is present in a text string.