[Leetcode] heap (31 questions in total)

[23] merge K sorted lists

[215] kth largest element in an array (minimum/maximum number of K in an unordered array)

Given an unordered array, there may be repeated numbers. Find the largest element at K and return this element value.

Question: directly use a heap to save the maximum K number in the array. The time complexity is O (nlogk ).

1 // the time complexity is O (nlogk), with heap assistance. 2 class solution {3 Public: 4 int findkthlargest (vector <int> & Nums, int K) {5 const int n = nums. size (); 6 priority_queue <int, vector <int>, greater <int> PQ; 7 for (INT I = 0; I <n; ++ I) {8 If (PQ. size () <k) {9 PQ. push (Nums [I]); 10} else {11 if (PQ. top () <Nums [I]) {12 PQ. pop (); 13 PQ. push (Nums [I]); 14} 15} 16} 17 return PQ. top (); 18} 19 };

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The O (n) solution can be provided for this question. For details, refer to "offoffoffer" or "Programmer code Interview Guide" p336.

 

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[703] kth largest element in a stream

Returns the maximum K element for a digital stream.

The solution is to use a heap with only k elements to maintain these numbers from the largest K to the largest element.

[Minimum element... the largest element in K... the largest element]. This heap maintains k elements in the second half.

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[719] Find k-th smallest pair distance

[743] Network Delay Time

[759] employee free time

[767] reorganize string

[778] Swim in rising water

[786] k-th smallest prime Fraction

[787] cheapest flights within K stops

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[857] minimum cost to hire K workers

[864] shortest path to get all keys

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[Leetcode] heap (31 questions in total)