class Solution { public: int Fibonacci(int n) { if (n == 1 || n == 2) { return 1; } int n1 = 1, n2 = 1, n3; for (int i = 3; i <= n; ++i) { n3 = n1 + n2; n1 = n2; n2 = n3; } return n3; } };
递推就行了