《剑指offer》第十天：青蛙跳台阶

f(n) = f(n-1) + f(n-2)

public class Solution {
    /**
     * 青蛙跳台阶
     * @param target 跳上的那一级台阶
     * @return 多少种跳法
     */
    public int JumpFloor(int target) {
        if (target < 3) {
            return target;
        }
        int[] res = new int[target + 1];
        res[1] = 1;
        res[2] = 2;
        for (int i = 3; i <= target; ++i) {
            res[i] = res[i - 1] + res[i - 2];
        }
        return res[target];
    }
}