Created Nth_Fib_number #hacktoberfest2019

Nth_Fib_number#hacktoberfest

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+#include <bits/stdc++.h> 
+using namespace std; 
+
+const int MAX = 10000; 
+
+int f[MAX] = {0}; 
+
+int fib(int n) //This soluton is in O(log n) time complexity
+{ 
+    if (n == 0) 
+        return 0; 
+    if (n == 1 || n == 2) 
+        return (f[n] = 1); 
+
+    if (f[n]) 
+        return f[n]; 
+
+    int k = (n & 1)? (n+1)/2 : n/2; 
+
+    f[n] = (n & 1)? (fib(k)*fib(k) + fib(k-1)*fib(k-1)) 
+           : (2*fib(k-1) + fib(k))*fib(k); 
+
+    return f[n]; 
+} 
+
+int main() 
+{ 
+    int n;
+    cout<<"Enter the nth fibbonacci numner you want to find ~ ";
+    cin>>n;
+    cout<<endl;
+    cout<<"The nth order fibbonacci number is ~ "<<fib(n);
+    return 0; 
+}