剑指OFFER----面试题13. 机器人的运动范围

链接：https://leetcode-cn.com/problems/ji-qi-ren-de-yun-dong-fan-wei-lcof/

思路：

　　dfs

代码：

class Solution {
public:
    int get_single_sum(int x) {
        int s= 0;
        while (x) {
            s += x % 10;
            x /= 10;
        }
        return s;
    }

    int get_sum(pair<int, int> p) {
        return get_single_sum(p.first) + get_single_sum(p.second);
    }

    int movingCount(int m, int n, int k) {
        int res = 0;
        if (!m || !n) return 0;
        vector<vector<bool>> st(m, vector<bool>(n, false));
        queue<pair<int, int>> q;
        int dx[4] = {-1, 0, 1, 0}, dy[4] = {0, 1, 0, -1};

        q.push({0, 0});
        while (q.size()) {
            auto t = q.front();
            q.pop();

            if (get_sum(t) > k || st[t.first][t.second]) continue;
            res++;
            st[t.first][t.second] = true;

            for (int i = 0; i < 4; ++i) {
                int x = t.first + dx[i], y = t.second + dy[i];
                if (x >= 0 && x < m && y >= 0 && y < n) {
                    q.push({x, y});
                }
            }
        }
        return res;
    }
};