题解 | #牛牛的循环牧场#

class Solution {
public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param nums int整型vector 
     * @return bool布尔型
     */
    int nextstep(vector<int>& nums, int curr_step){
        int temp = (curr_step + nums[curr_step]);
        if ( temp  < 0) {
            curr_step = temp + nums.size();
        }
        else if( temp >= nums.size()){
            curr_step = (temp - nums.size());
        }
        else {
            curr_step = temp;
        }
        return curr_step;
    }

    bool get_sign(int num){
        if (num < 0)  return false;
        else return true;
    }

    bool set_state(int index, vector<int>& nums, vector<bool>& state, bool sign){
        state[index] = true;
        int next = nextstep(nums, index);
        if ((sign ^ get_sign(nums[next]))) return false;
        if (next == index) return false;
        if (state[next] == true) return true;
        return set_state(next, nums, state, sign);
    }

    bool checkCircularArray(vector<int>& nums) {
        // write code here
        for(int i = 0; i < nums.size(); ++i){
                vector<bool> state(nums.size(), false);
                bool sign = get_sign(nums[i]);
                if (set_state(i, nums, state, sign)) return true;
        }
        return false;
    }
};