剑指Offer LeetCode 面试题10- I. 斐波那契数列

 public int fib(int n) {
     int a = 0,b = 1,sum=0;
     for (int i = 0; i < n ; i++) {
         sum = (a+b) % 1000000007;
         a = b;
         b = sum;
     }
     return a;
}

  public int fib2(int n) {
        if(n==0 || n==1)
            return n;

        int nArr[] = new int[n];
        nArr[0]=0;
        nArr[1]=1;

        for (int i = 2; i < n ; i++) {
            nArr[i] = (nArr[i - 1] + nArr[i - 2]) % 1000000007;
        }

        return (nArr[n - 1] + nArr[n - 2]) % 1000000007;
    }