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Author: black-shadows

Time Complexity/Count Palindromic Subsequences.cpp

@@ -0,0 +1,45 @@
+int Solution::solve(string A) {
+long long mod = 1000000007;
+int n;
+n = A.length();
+if(n==1)
+{
+return 1;
+}
+long long dp[n+1][n+1];
+for(int i=0;i<=n;i++)
+{
+for(int j=0;j<=n;j++)
+{
+dp[i][j] = 0;
+}
+}
+for(int i = 0; i<n;i++)
+{
+dp[i][i] = 1;
+}
+for(int i=0;i<n-1;i++)
+{
+if(A[i] == A[i+1])
+{
+dp[i][i+1] = 3;
+}
+else
+{
+dp[i][i+1] = 2;
+}
+}
+for(int i=3;i<=n;i++)
+{
+for(int j=0;i+j-1<n;j++)
+{
+long long a = 0;
+if(A[j] == A[i+j-1])
+{
+a = 1;
+}
+dp[j][i+j-1] = (((dp[j + 1][i + j - 1]%mod) + (dp[j][i + j - 2] - dp[j + 1][i + j - 2])%mod)%mod + ((a) * (dp[j + 1][i + j - 2]+1))%mod)%mod;
+}
+}
+return dp[0][n-1]%mod;
+}

Time Complexity/Find subsequence.cpp

@@ -0,0 +1,22 @@
+string Solution::solve(string A, string B) {
+    int m = A.length();
+    int n = B.length();
+    int i=0,j=0;
+    while(i<m && j<n)
+    {
+        if(A[i] == B[j])
+        {
+            i++;
+            j++;
+        }
+        else
+        {
+            j++;
+        }
+    }
+    if(i == m)
+    {
+        return "YES";
+    }
+    return "NO";
+}

Time Complexity/Longest Palindromic Substring.cpp

@@ -0,0 +1,15 @@
+string Solution::longestPalindrome(string s) {
+    if (s.empty()) return "";
+    if (s.size() == 1) return s;
+    int min_start = 0, max_len = 1;
+    for (int i = 0; i < s.size();) {
+      if (s.size() - i <= max_len / 2) break;
+      int j = i, k = i;
+      while (k < s.size()-1 && s[k+1] == s[k]) ++k; // Skip duplicate characters.
+      i = k+1;
+      while (k < s.size()-1 && j > 0 && s[k + 1] == s[j - 1]) { ++k; --j; } // Expand.
+      int new_len = k - j + 1;
+      if (new_len > max_len) { min_start = j; max_len = new_len; }
+    }
+    return s.substr(min_start, max_len);
+}

Time Complexity/Matrix Permutation.cpp

@@ -0,0 +1,23 @@
+string Solution :: solve(vector <vector <int> > &A)
+{
+    int n = A.size();
+    string temp = "";
+    for (int i = 0 ; i < n ; i++)
+    {
+        temp = temp + "-" + to_string(A[0][i]);
+    }
+    temp += temp;
+    for (int i=1; i<n; i++)
+    {
+        string s = "";
+        for (int j = 0 ; j < n ; j++)
+            {
+             s = s + "-" + to_string(A[i][j]);
+            }
+        if (temp.find(s) == string::npos)
+        {
+            return "NO";
+        }
+    }
+    return "YES";
+}