[LeetCode] 954. Array of Doubled Pairs 涓ゅ€嶆暟瀵瑰効鏁扮粍

Posted 2020-12-18

鏍囩锛?a href='http://www.mamicode.com/so/1/ems' title='ems'>ems   issue   oss   als   code   log   https   example   NPU   

Given an array of integers?A?with even length, return?true?if and only if it is possible to reorder it such that?A[2 * i + 1] = 2 * A[2 * i]?for every?0 <=?i < len(A) / 2.

Example 1:

Input: [3,1,3,6]
Output: false

Example 2:

Input: [2,1,2,6]
Output: false

Example 3:

Input: [4,-2,2,-4]
Output: true
Explanation: We can take two groups, [-2,-4] and [2,4] to form [-2,-4,2,4] or [2,4,-2,-4].

Example 4:

Input: [1,2,4,16,8,4]
Output: false

Note:

1. 0 <= A.length <= 30000
2. A.length?is even
3. -100000 <= A[i] <= 100000

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瑙ｆ硶涓€锛?/p>

class Solution {
public:
    bool canReorderDoubled(vector<int>& A) {
        unordered_map<int, int> m;
        for (int num : A) ++m[num];
        vector<int> keys;
        for (auto &a : m) keys.push_back(a.first);
        sort(keys.begin(), keys.end(), [](int i, int j) {return abs(i) < abs(j);});
        for (int key : keys) {
            if (m[key] > m[2 * key]) return false;
            m[2 * key] -= m[key];
        }
        return true;
    }
};

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瑙ｆ硶浜岋細

class Solution {
public:
    bool canReorderDoubled(vector<int>& A) {
        map<int, int> m;
        for (int num : A) ++m[num];
        for (auto &a : m) {
            if (a.second == 0) continue;
            int want = a.first < 0 ? a.first / 2 : a.first * 2;
            if ((a.first < 0 && a.first % 2 != 0) || a.second > m[want]) return false;
            m[want] -= a.second;
        }
        return true;
    }
};

Github 鍚屾鍦板潃:

https://github.com/grandyang/leetcode/issues/954

鍙傝€冭祫鏂欙細

https://leetcode.com/problems/array-of-doubled-pairs/

https://leetcode.com/problems/array-of-doubled-pairs/discuss/209564/Java-Heap-Concise

https://leetcode.com/problems/array-of-doubled-pairs/discuss/203183/JavaC%2B%2BPython-Match-from-the-Smallest-or-Biggest-100

LeetCode All in One 棰樼洰璁茶В姹囨€?鎸佺画鏇存柊涓?..)