longestCommonSubstring.cpp created

Dynamic Programming/longestCommonSubstring.cpp

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+// Problem : A substring of a string is a subsequence in which all the characters are consecutive.Given two strings,
+// we need to find the longest common substring.
+
+// Approach :
+
+// We are creating a 2d dp array corresponding to the dimensions of the array. Now if the characters for a pair of
+// i, j are not equal, that show that they can be included in the final answer and hence they are discarded.
+// Else, we take a look at dp[i-1][j-1] if the continuity is maintained the we can find a continous equal substring
+// or not.
+
+#include <bits/stdc++.h>
+using namespace std;
+
+int lcs(string &s1, string &s2)
+{
+    int n = s1.size();
+    int m = s2.size();
+    vector<vector<int>> dp(n + 1, vector<int>(m + 1, 0));
+    int ans = 0;
+    for (int i = 1; i <= n; i++)
+    {
+        for (int j = 1; j <= m; j++)
+        {
+            if (s1[i - 1] == s2[j - 1])
+            {
+                // looking if just previous characters are also equal or not
+                int val = 1 + dp[i - 1][j - 1];
+                dp[i][j] = val;
+                ans = max(ans, val);
+            }
+            else
+            {
+                // not a part of equal substring, hence 0
+                dp[i][j] = 0;
+            }
+        }
+    }
+    return ans;
+}
+
+int main()
+{
+    string s1;
+    string s2;
+    cin >> s1 >> s2;
+    cout << "The Length of Longest Common Substring is " << lcs(s1, s2);
+}
+
+// Sample Inputs
+
+// abcjklp
+// acjkp
+
+// Corresponding Outputs
+
+// 3