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| 1 | +// Source : https://leetcode.com/problems/queue-reconstruction-by-height/ |
| 2 | +// Author : Hao Chen |
| 3 | +// Date : 2016-11-12 |
| 4 | + |
| 5 | +/*************************************************************************************** |
| 6 | + * |
| 7 | + * Suppose you have a random list of people standing in a queue. Each person is |
| 8 | + * described by a pair of integers (h, k), where h is the height of the person and k is |
| 9 | + * the number of people in front of this person who have a height greater than or equal |
| 10 | + * to h. Write an algorithm to reconstruct the queue. |
| 11 | + * |
| 12 | + * Note: |
| 13 | + * The number of people is less than 1,100. |
| 14 | + * |
| 15 | + * Example |
| 16 | + * |
| 17 | + * Input: |
| 18 | + * [[7,0], [4,4], [7,1], [5,0], [6,1], [5,2]] |
| 19 | + * |
| 20 | + * Output: |
| 21 | + * [[5,0], [7,0], [5,2], [6,1], [4,4], [7,1]] |
| 22 | + ***************************************************************************************/ |
| 23 | + |
| 24 | +class Solution { |
| 25 | + |
| 26 | +public: |
| 27 | + vector<pair< int, int>> reconstructQueue(vector<pair< int, int>>& people) { |
| 28 | + //sort function |
| 29 | + auto comp = [](const pair<int, int>& p1, const pair<int, int>& p2) |
| 30 | + { return p1.first == p2.first ? p1.second < p2.second : p1.first > p2.first; }; |
| 31 | + //sort the people with their height with descending order |
| 32 | + // and if the height is same then sort by K with ascending order |
| 33 | + sort(people.begin(), people.end(), comp); |
| 34 | + |
| 35 | + // For example: |
| 36 | + // Original Queue: [7,0], [4,4], [7,1], [5,0], [6,1], [5,2] |
| 37 | + // Sorted Queue: [7,0], [7,1], [6,1], [5,0], [5,2], [4,4] |
| 38 | + |
| 39 | + |
| 40 | + // Why do we need to sort like this? |
| 41 | + // |
| 42 | + // ** The position of shorter people is ZERO impacted with higher people. ** |
| 43 | + // |
| 44 | + // and, the shortest people has no impacts to all of people. we can simpley insert it to the Kth position |
| 45 | + // |
| 46 | + // So, we sorted the people from highest to the shortest, then when we insert the people to another array, |
| 47 | + // |
| 48 | + // we always can guarantee the people is going to be inserted has nothing to do with the people has been inserted. |
| 49 | + // |
| 50 | + // Let's continue the about example above |
| 51 | + // |
| 52 | + // [7,0] => [] then [7,0] |
| 53 | + // [7,1] => [7,0] then [7,0], [7,1] |
| 54 | + // [6,1] => [7,0], [7,1] then [7,0], [6,1], [7,1] |
| 55 | + // [5,0] => [7,0], [6,1], [7,1] then [5,0], [7,0], [6,1], [7,1] |
| 56 | + // [5,2] => [5,0], [7,0], [6,1], [7,1] then [5,0], [7,0], [5,2], [6,1], [7,1] |
| 57 | + // [4,4] => [5,0], [7,0], [5,2], [6,1], [7,1] then [5,0], [7,0], [5,2], [6,1], [4,4], [7,1] |
| 58 | + // |
| 59 | + // We alway can see, the people is going to be inserted has NO IMPACT with the current people. |
| 60 | + // |
| 61 | + // [6,1] => [7,0], [7,1] |
| 62 | + // |
| 63 | + // Whatever the people[6,1] placed, it has nothing to do with the people [7,0] [7,1], |
| 64 | + // So, we can just insert the people to the place he like - the `Kth` place. |
| 65 | + // |
| 66 | + // |
| 67 | + vector<pair<int, int>> res; |
| 68 | + for (auto& p : people) { |
| 69 | + res.insert(res.begin() + p.second, p); |
| 70 | + } |
| 71 | + return res; |
| 72 | + } |
| 73 | +}; |
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