1743. 从相邻元素对还原数组

class Solution {
    public int[] restoreArray(int[][] adjacentPairs) {
        //1和4在二维数组中出现1次  其它出现2次
        //先统计次数，然后找到出现1次的数字1
        //然后找2的相邻元素3
        //然后找3的相邻元素4
        //遍历一遍数组，构造一个HashMap<Integer,List<Integer>>
        HashMap<Integer, List<Integer>> map = new HashMap<>();
        HashSet<Integer> set = new HashSet<>();
        for(int i=0;i<adjacentPairs.length;i++){
            for (int j = 0; j < 2; j++) {
                int key = adjacentPairs[i][j];
                int adjKey = adjacentPairs[i][1-j];
                if(!map.containsKey(key)) {
                    List<Integer> list = new ArrayList<>();
                    list.add(adjKey);
                    System.out.println(adjKey);
                    map.put(key, list);
                }
                else {
                    map.get(key).add(adjKey);
                }
            }

        }
        //System.out.println(map);
        int[] res = new int[map.size()];
        int idx=0,e=0;
        for (Integer key : map.keySet()) {
            List<Integer> list = map.get(key);
            if(list.size()==1){
                //System.out.println(key);
                res[idx++]=key;
                set.add(key);
                e=key;
                break;
            }
        }
        //System.out.println(map.get(1).get(0));
        while (set.size()!=map.size()){
            List<Integer> list = map.get(e);
            System.out.println(list);
            for (Integer integer : list) {
                if(!set.contains(integer)){
                    System.out.println(integer);
                    res[idx++] = integer;
                    set.add(integer);
                    e = integer;
                }
            }
        }
        return res;
    }
}

标签：map,数组,int,list,System,相邻,key,out,1743
来源： https://blog.csdn.net/qq_39370495/article/details/119081590