LeetCode-Climbing Stairs

斐波那契数列；

class Solution {
public:
    int climbStairs(int n) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        if (n <= 0) {
            return 0;
        }
        vector<int> fb(n + 1, 1);
        fb[2] = 2;
        for (int i = 3; i <= n; ++i) {
            fb[i] = fb[i - 1] + fb[i - 2];
        }
        return fb[n];
    }
};