Merge pull request #139 from aryanandarnav13/patch-4

Create longest_common_subsequence.cpp

Author: sunnyshahabuddin

longest_common_subsequence.cpp

@@ -0,0 +1,80 @@
+#include <iostream>
+#include <vector>
+#include <string>
+
+using namespace std;
+
+// Function to find the length of the Longest Common Subsequence
+int longestCommonSubsequenceLength(const string& str1, const string& str2) {
+    int m = str1.length();
+    int n = str2.length();
+
+    // Create a 2D table to store the length of LCS
+    vector<vector<int>> dp(m + 1, vector<int>(n + 1, 0));
+
+    // Fill the table using DP
+    for (int i = 1; i <= m; i++) {
+        for (int j = 1; j <= n; j++) {
+            if (str1[i - 1] == str2[j - 1]) {
+                dp[i][j] = dp[i - 1][j - 1] + 1;
+            } else {
+                dp[i][j] = max(dp[i - 1][j], dp[i][j - 1]);
+            }
+        }
+    }
+
+    return dp[m][n];
+}
+
+// Function to find the Longest Common Subsequence
+string longestCommonSubsequence(const string& str1, const string& str2) {
+    int m = str1.length();
+    int n = str2.length();
+
+    vector<vector<int>> dp(m + 1, vector<int>(n + 1, 0));
+
+    for (int i = 1; i <= m; i++) {
+        for (int j = 1; j <= n; j++) {
+            if (str1[i - 1] == str2[j - 1]) {
+                dp[i][j] = dp[i - 1][j - 1] + 1;
+            } else {
+                dp[i][j] = max(dp[i - 1][j], dp[i][j - 1]);
+            }
+        }
+    }
+
+    int length = dp[m][n];
+    string lcs(length, ' ');
+
+    int i = m, j = n;
+    while (i > 0 && j > 0) {
+        if (str1[i - 1] == str2[j - 1]) {
+            lcs[length - 1] = str1[i - 1];
+            i--;
+            j--;
+            length--;
+        } else if (dp[i - 1][j] > dp[i][j - 1]) {
+            i--;
+        } else {
+            j--;
+        }
+    }
+
+    return lcs;
+}
+
+int main() {
+    string str1, str2;
+    cout << "Enter the first string: ";
+    cin >> str1;
+    cout << "Enter the second string: ";
+    cin >> str2;
+
+    int length = longestCommonSubsequenceLength(str1, str2);
+    cout << "Length of Longest Common Subsequence: " << length << endl;
+
+    string lcs = longestCommonSubsequence(str1, str2);
+    cout << "Longest Common Subsequence: " << lcs << endl;
+
+    return 0;
+}