Longest Common Subsequence with subsequence printing

Dynamic Programming/Longest Common Subsequence.cpp

@@ -1,23 +1,71 @@
 //Longest common subsequence - Dynamic Programming
 #include <iostream>
 using namespace std;
+
+void Print(int trace[20][20], int m, int n, string a)
+{
+	if (m==0 || n==0)
+	{
+		return;
+	}
+	if (trace[m][n]==1)
+	{
+		Print(trace, m-1, n-1, a);
+		cout<<a[m-1];
+	}
+	else if(trace[m][n]==2)
+	{
+		Print(trace, m-1,n, a);
+	}
+	else if (trace[m][n]==3)
+	{
+		Print(trace, m,n-1, a);
+	}
+}
+
+
+
 int lcs(string a, string b){
 	int m = a.length(), n = b.length();
 	int res[m+1][n+1];
+	int trace[20][20];
 	for (int i = 0; i < m+1; ++i)
 	{
 		for (int j = 0; j < n+1; ++j)
 		{
 			if(i==0||j==0)
-				res[i][j] = 0;
+				{
+					res[i][j] = 0;	
+					trace[i][j]=0;
+				}
+				
 			else if(a[i-1]==b[j-1])
+			{
 				res[i][j] = 1 + res[i-1][j-1];
+				trace[i][j]=1;			// 1 means trace the matrix in upper left diagonal direction.
+			}
 			else
-				res[i][j] = max(res[i-1][j], res[i][j-1]);
+			{
+				if (res[i-1][j]>res[i][j-1])
+				{
+					res[i][j]=res[i-1][j];
+					trace[i][j]=2;		// 2 means trace the matrix in upwards direction.
+				}
+				else
+				{
+					res[i][j]=res[i][j-1];
+					trace[i][j]=3;		//  means trace the matrix in left direction.
+				}	
+			}
 		}
 	}
+	Print(trace, m, n, a);
 	return res[m][n];
 }
+
+
+
+
 int main()
 {
 	string a,b;