C++ LCS algorithm added

c++/Longest_Common_Subsequence.cpp

@@ -0,0 +1,40 @@
+/*Longest Common Subsequence Algorithm*/
+
+#include <bits/stdc++.h>
+using namespace std;
+
+#define ll             long long 
+#define int            long long
+#define pb             push_back
+#define endl           "\n"
+#define F              first
+#define S              second
+#define popcount(x)    __builtin_popcountll(x)
+typedef unsigned long long ull;
+
+
+const int M=1000000007;
+const int MM=998244353;
+const int INF =9e18;
+
+int lcs(string a,string b,int m,int n)
+{
+   if(m==0||n==0)
+    return 0;
+   if(a[m-1]==b[n-1])
+    return (1LL+lcs(a,b,m-1,n-1));
+   int x=lcs(a,b,m,n-1);
+   int y=lcs(a,b,m-1,n);
+   return max(x,y);
+
+}
+signed main()
+{
+    string a,b;
+    cin>>a>>b;
+    int m=a.size(),n=b.size();
+    int ans=lcs(a,b,m,n);
+    cout<<"Length of Longest common subsequence of "<<a<<" and "<<b<<" is :"<<ans;
+}
+
+/*_*/