Fibonacci: A 64-Bit Example - C++ STL

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Description

Fibonacci: A 64-Bit Example

Demo Code

#include <iostream>
#include <string>
#include <sstream>
using namespace std;
int long long Fibo(int n);
string output_formatted_string(long long num);
int main() {//from w  ww.ja  v a 2s  .  c  o  m
  int n = 0;
  cout << "Enter a number: ";
  cin >> n;
  string s = output_formatted_string(Fibo(n));
  cout << "Fibo(" << n << ") = " << s << endl;
  return 0;
}
long long Fibo(int n) {
  if (n < 2)
    return 1;
  long long temp1 = 1;
  long long temp2 = 1;
  long long total = 0;
  while (n-- > 1) {
    total = temp1 + temp2;
    temp2 = temp1;
    temp1 = total;
  }
  return total;
}

string output_formatted_string(long long num) {
  int GROUP_SIZE = 3;
  char GROUP_SEP = ',';
  // Read data into string s.
  stringstream temp, out;
  temp << num;
  string s = temp.str();
  int n = s.size() % GROUP_SIZE;
  int i = 0;
  if (n > 0 && s.size() > GROUP_SIZE) {
    out << s.substr(i, n) << GROUP_SEP;
    i += n;
  }
  // Handle all the remaining groups.
  n = s.size() / GROUP_SIZE - 1;
  while (n-- > 0) {
    out << s.substr(i, GROUP_SIZE) << GROUP_SEP;
    i += GROUP_SIZE;
  }
  out << s.substr(i); // Write the rest of digits.
  return out.str();   // Convert stream -> string.
}

Result


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