#1594 Added Needleman-Wunsch Algorithm

String Algorithms/Needleman-Wunsch Algorithm/Program.c

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+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+
+#define MATCH 1   // Score for a match
+#define MISMATCH -1 // Score for a mismatch
+#define GAP -2     // Penalty for a gap
+
+// Function to calculate the maximum of three values
+int max(int a, int b, int c) {
+    if (a >= b && a >= c) return a;
+    else if (b >= a && b >= c) return b;
+    else return c;
+}
+
+// Function to implement the Needleman-Wunsch algorithm
+void needlemanWunsch(char* seq1, char* seq2) {
+    int len1 = strlen(seq1);
+    int len2 = strlen(seq2);
+
+    // Initialize score matrix
+    int scoreMatrix[len1 + 1][len2 + 1];
+
+    // Initialize first row and first column with gap penalties
+    for (int i = 0; i <= len1; i++) {
+        scoreMatrix[i][0] = i * GAP;
+    }
+    for (int j = 0; j <= len2; j++) {
+        scoreMatrix[0][j] = j * GAP;
+    }
+
+    // Fill the score matrix
+    for (int i = 1; i <= len1; i++) {
+        for (int j = 1; j <= len2; j++) {
+            int matchMismatchScore = (seq1[i - 1] == seq2[j - 1]) ? MATCH : MISMATCH;
+            scoreMatrix[i][j] = max(
+                scoreMatrix[i - 1][j - 1] + matchMismatchScore, // Match/Mismatch
+                scoreMatrix[i - 1][j] + GAP,                    // Deletion (gap in seq2)
+                scoreMatrix[i][j - 1] + GAP                     // Insertion (gap in seq1)
+            );
+        }
+    }
+
+    // Print the final score matrix
+    printf("Score Matrix:\n");
+    for (int i = 0; i <= len1; i++) {
+        for (int j = 0; j <= len2; j++) {
+            printf("%3d ", scoreMatrix[i][j]);
+        }
+        printf("\n");
+    }
+
+    // Traceback to get the optimal alignment
+    printf("\nOptimal Alignment:\n");
+    int i = len1, j = len2;
+    char alignedSeq1[len1 + len2 + 1], alignedSeq2[len1 + len2 + 1];
+    int idx = 0;
+
+    while (i > 0 || j > 0) {
+        if (i > 0 && j > 0 && scoreMatrix[i][j] == scoreMatrix[i - 1][j - 1] + ((seq1[i - 1] == seq2[j - 1]) ? MATCH : MISMATCH)) {
+            alignedSeq1[idx] = seq1[i - 1];
+            alignedSeq2[idx] = seq2[j - 1];
+            i--; j--;
+        }
+        else if (i > 0 && scoreMatrix[i][j] == scoreMatrix[i - 1][j] + GAP) {
+            alignedSeq1[idx] = seq1[i - 1];
+            alignedSeq2[idx] = '-';
+            i--;
+        }
+        else {
+            alignedSeq1[idx] = '-';
+            alignedSeq2[idx] = seq2[j - 1];
+            j--;
+        }
+        idx++;
+    }
+
+    // Print aligned sequences
+    alignedSeq1[idx] = '\0';
+    alignedSeq2[idx] = '\0';
+
+    // Reverse the sequences
+    for (int k = 0; k < idx / 2; k++) {
+        char temp = alignedSeq1[k];
+        alignedSeq1[k] = alignedSeq1[idx - k - 1];
+        alignedSeq1[idx - k - 1] = temp;
+
+        temp = alignedSeq2[k];
+        alignedSeq2[k] = alignedSeq2[idx - k - 1];
+        alignedSeq2[idx - k - 1] = temp;
+    }
+
+    printf("Seq1: %s\n", alignedSeq1);
+    printf("Seq2: %s\n", alignedSeq2);
+}
+
+int main() {
+    char seq1[] = "GATTACA";
+    char seq2[] = "GCATGCU";
+
+    printf("Sequence 1: %s\n", seq1);
+    printf("Sequence 2: %s\n", seq2);
+
+    needlemanWunsch(seq1, seq2);
+
+    return 0;
+}

String Algorithms/Needleman-Wunsch Algorithm/README.md

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+# Needleman-Wunsch Algorithm
+
+## Description
+
+The Needleman-Wunsch algorithm is a dynamic programming algorithm used for sequence alignment. It is particularly useful for aligning nucleotide or protein sequences in bioinformatics but can also be applied to string matching in computer science.
+
+### Problem Definition
+
+Given:
+- Two sequences (or strings) **S1** and **S2**
+
+Objective:
+- Align the two sequences by introducing gaps (if necessary) to maximize the match score while minimizing the penalty for mismatches and gaps.
+
+### Algorithm Overview
+
+1. **Initialize Score Matrix**: 
+   - Create a score matrix with dimensions `(len(S1) + 1)` x `(len(S2) + 1)` and initialize the first row and column with gap penalties.
+2. **Matrix Filling**: 
+   - Fill the matrix by choosing the optimal score for each cell based on the previous cells, using:
+     - Match/Mismatch score
+     - Insertion/Deletion (gap) score
+3. **Traceback**: 
+   - Trace back through the matrix to determine the optimal alignment of the two sequences.
+
+### Key Features
+
+- Global alignment algorithm
+- Handles mismatches and gaps with penalties
+- Constructs an optimal alignment based on a scoring system
+- Suitable for aligning sequences of varying lengths
+
+### Time Complexity
+
+- **Time Complexity**: O(m * n), where `m` is the length of sequence S1, and `n` is the length of sequence S2. This is due to the need to fill in a score matrix of size `m x n`.
+- **Space Complexity**: O(m * n), due to the storage required for the score matrix.
+
+### Scoring
+
+- **Match**: +1 (reward for matching characters)
+- **Mismatch**: -1 (penalty for different characters)
+- **Gap**: -2 (penalty for inserting gaps)
+
+## Implementation
+
+The implementation in C demonstrates the Needleman-Wunsch algorithm for aligning two sequences. It includes:
+
+1. **Score Matrix Calculation**: Initializes and fills the score matrix based on matches, mismatches, and gaps.
+2. **Traceback**: Recovers the optimal alignment by tracing back through the score matrix.
+3. **Alignment Output**: Prints the aligned sequences.
+
+## Usage
+
+1. **Compile**: Use a C compiler to compile the program.
+   ```bash
+   gcc needleman_wunsch.c -o needleman_wunsch
+   ```
+
+2. **Run**: Execute the program with two predefined sequences.
+   ```bash
+   ./needleman_wunsch
+   ```
+
+The example in the `main` function aligns the sequences "GATTACA" and "GCATGCU" and prints the optimal alignment and the corresponding score matrix.