代码随想录 Leetcode332. 重新安排行程

题目：

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代码(首刷看解析 2024年2月6日）：

class Solution {
private:
    unordered_map> targets;
public:
    bool backtracking(int tickNum, vector& res) {
        if (tickNum == res.size() - 1) {
            return true;
        }
        for (pair& target : targets[res[res.size() - 1]]) {
            if (target.second > 0) {
                res.push_back(target.first);
                target.second--;
                if (backtracking(tickNum, res)) return true;
                target.second++;
                res.pop_back();
            }
        }
        return false;
    }
    vector findItinerary(vector>& tickets) {
        targets.clear();
        vector res;
        for (const vector& vec : tickets) {
            targets[vec[0]][vec[1]]++;
        }
        res.push_back("JFK");
        backtracking(tickets.size(), res);
        return res;
    }
};