fibonacci-number.java

class Solution {
  public int fib(int n) {
    if (n == 0) {
      return 0;
    }
    int curr = 1;
    int first = 0;
    int second = 1;

    for (int i = 2; i <= n; i++) {
      curr = first + second;
      first = second;
      second = curr;
    }

    return curr;
  }
}