Create Longest common substring - DP.cpp

Author: nikolatechie

Longest common substring - DP.cpp

@@ -0,0 +1,70 @@
+// Dynamic programming solution
+#include <bits/stdc++.h>
+#include <ext/rope>
+using namespace std;
+using namespace __gnu_cxx;
+
+using ld = long double;
+using llint = long long;
+using ullint = unsigned long long;
+using pii = pair <int,int>;
+using pcc = pair <char,char>;
+using pss = pair <string,string>;
+using vi = vector <int>;
+using vb = vector <bool>;
+using vii = vi::iterator;
+
+#define INF (1<<30)
+#define MOD 1000000007
+#define mp make_pair
+#define mt make_tuple
+#define all(c) c.begin(), c.end()
+#define ms(name,val) memset(name, val, sizeof name)
+#define np nullptr
+
+
+int n, m;
+string a, b;
+vector <vi> DP;
+
+int longestCommonSubstring()
+{
+    int ans = 0;
+    DP.resize(n);
+
+    for (int t1 = 0; t1 < n; ++t1)
+    {
+        DP[t1].resize(m);
+        DP[t1][0] = (a[t1] == b[0]);
+    }
+
+    for (int t2 = 0; t2 < m; ++t2)
+        DP[0][t2] = (a[0] == b[t2]);
+
+    for (int t1 = 1; t1 < n; ++t1)
+    {
+        for (int t2 = 1; t2 < m; ++t2)
+        {
+            if (a[t1] == b[t2])
+            {
+                DP[t1][t2] = 1 + DP[t1-1][t2-1];
+                ans = max(ans, DP[t1][t2]);
+            }
+        }
+    }
+
+    return ans;
+}
+
+int main()
+{
+    ios_base::sync_with_stdio(0);
+    //cin.tie(0);
+
+    cin >> a >> b;
+    n = a.size(), m = b.size();
+    cout << longestCommonSubstring() << '\n';
+
+
+    return 0;
+}