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14.LCS.cpp

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+/*
+ * This program applies LC algorithm on two string user enters
+ *
+ *      Coded by: Abdurrezak EFE
+ * */
+
+#include <iostream>
+#include <algorithm>
+#include <string>
+#include <stdio.h>
+using namespace std;
+
+int d[10000][10000]; // dynamic programming table
+
+string reverser(string str)
+{
+    string s="";
+    for(int i = str.size()-1;i>-1;i--)
+        s+=str[i];
+    return s;
+}
+
+string LCS(string s1, string s2)
+{
+    for(int i=0;i<s1.size();i++) // initiating first row as zeros
+        d[0][i] = 0;
+
+    for(int i=0;i<s2.size();i++) // initiating first column as zero
+        d[i][0] = 0;
+
+    for(int i=1; i<=s1.size(); i++)
+        for(int j=1; j<=s2.size(); j++)
+            if(s1[i-1] == s2[j-1])
+                d[i][j] = max(max(d[i-1][j-1]+1, d[i-1][j]),d[i][j-1]);
+            else
+                d[i][j] = max(d[i-1][j], d[i][j-1]);
+
+
+    string str=""; //getting lcs of s1 and s2
+    int i,j;
+    i = s1.size();
+    j = s2.size();
+
+    while(i>0 && j>0) //traceback for the string
+        if(d[i][j] == 1+d[i-1][j-1] && s1[i-1] == s2[j-1]) //if it was a match
+            str += s1[i-1], i--, j--;
+        else if(d[i][j-1] == d[i][j]) //if it was an insert
+            j--;
+        else if(d[i-1][j] == d[i][j]) //if it was a delete
+            i--;
+
+    return reverser(str);
+}
+
+int main()
+{
+    string s1,s2;
+
+    cin >> s1 >> s2;
+
+    cout << "The Longest Common Subsequence of " << s1 << " and " << s2 << " is: " << endl
+         <<LCS(s1,s2) << endl;
+}