improved the code

Author: Christian Bender

Dynamic Programming/Longest Common Subsequence.cpp

@@ -4,72 +4,84 @@ 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);
-	}
+    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;	
-					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
-			{
-				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 lcs(string a, string b)
+{
+    int m = a.length(), n = b.length();
+    int res[m+1][n+1];
+    int trace[20][20];
+
+    // fills up the arrays with zeros.
+    for (int i = 0; i < m+1; i++)
+    {
+        for (int j = 0; j < n+1; j++)
+        {
+            res[i][j] = 0;
+            trace[i][j] = 0;
+        }
+    }
+
+    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;
+                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
+            {
+                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;
-	cin>>a>>b;
-	cout<<lcs(a,b);
-	return 0;
+    string a,b;
+    cin>>a>>b;
+    cout<<lcs(a,b);
+    return 0;
 }