get fibonacci using memoization and dynamic programming

fibonacci.cpp

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+#include <iostream>
+using namespace std;
+
+int fibonacci(int num)
+{
+    if (num <= 1)
+    {
+        return num;
+    }
+    int a = fibonacci(num - 1);
+    int b = fibonacci(num - 2);
+    return a + b;
+}
+
+int fibonacci_mem_helper(int n, int *ans)
+{
+    if (n <= 1)
+    {
+        return n;
+    }
+    if (ans[n] != -1)
+    {
+        return ans[n];
+    }
+    int a = fibonacci_mem_helper(n - 1, ans);
+    int b = fibonacci_mem_helper(n - 2, ans);
+    ans[n] = a + b;
+    return ans[n];
+}
+
+int fibonacci_mem(int n)
+{
+    int *ans = new int[n + 1];
+    for (int i = 0; i <= n; i++)
+    {
+        ans[i] = -1;
+    }
+    return fibonacci_mem_helper(n, ans);
+}
+
+int fibo_3(int n)
+{
+    int *ans = new int[n + 1];
+    ans[0] = 0;
+    ans[1] = 1;
+    for (int i = 2; i <= n; i++)
+    {
+        ans[i] = ans[i - 1] + ans[i - 2];
+    }
+    return ans[n];
+}
+int main()
+{
+    cout << fibonacci_mem(6);
+}