algorithm

问题 This is the Triangle problem from Codility: A zero-indexed array A consisting of N integers is given. A triplet (P, Q, R) is triangular if 0 ≤ P < Q < R < N and: A[P] + A[Q] > A[R], A[Q] + A[R] > A[P], A[R] + A[P] > A[Q]. Write a function: int solution(vector<int> &A); that, given a zero-indexed array A consisting of N integers, returns 1 if there exists a triangular triplet for this array and returns 0 otherwise. For example, given array A such that: A[0] = 10, A[1] = 2, A[2] = 5, A[3] = 1,

问题 According to this cplusplus.com page, std::copy is in the <algorithm> header, as is std::swap and yet this works: #include <iostream> // std::cout #include <vector> // std::vector #include <iterator> // std::ostream_iterator() #include <cstdlib> // rand(), srand() // NOT including <algorithm> int main() { srand(time(NULL)); const int SIZE = 10; std::vector<int> vec; for(int i = 0; i < SIZE; ++i) { vec.push_back(rand() % 256); } copy(vec.begin(), vec.end(), std::ostream_iterator<int>(std::cout

问题 According to this cplusplus.com page, std::copy is in the <algorithm> header, as is std::swap and yet this works: #include <iostream> // std::cout #include <vector> // std::vector #include <iterator> // std::ostream_iterator() #include <cstdlib> // rand(), srand() // NOT including <algorithm> int main() { srand(time(NULL)); const int SIZE = 10; std::vector<int> vec; for(int i = 0; i < SIZE; ++i) { vec.push_back(rand() % 256); } copy(vec.begin(), vec.end(), std::ostream_iterator<int>(std::cout

问题 According to this cplusplus.com page, std::copy is in the <algorithm> header, as is std::swap and yet this works: #include <iostream> // std::cout #include <vector> // std::vector #include <iterator> // std::ostream_iterator() #include <cstdlib> // rand(), srand() // NOT including <algorithm> int main() { srand(time(NULL)); const int SIZE = 10; std::vector<int> vec; for(int i = 0; i < SIZE; ++i) { vec.push_back(rand() % 256); } copy(vec.begin(), vec.end(), std::ostream_iterator<int>(std::cout

问题 According to this cplusplus.com page, std::copy is in the <algorithm> header, as is std::swap and yet this works: #include <iostream> // std::cout #include <vector> // std::vector #include <iterator> // std::ostream_iterator() #include <cstdlib> // rand(), srand() // NOT including <algorithm> int main() { srand(time(NULL)); const int SIZE = 10; std::vector<int> vec; for(int i = 0; i < SIZE; ++i) { vec.push_back(rand() % 256); } copy(vec.begin(), vec.end(), std::ostream_iterator<int>(std::cout

问题 According to this cplusplus.com page, std::copy is in the <algorithm> header, as is std::swap and yet this works: #include <iostream> // std::cout #include <vector> // std::vector #include <iterator> // std::ostream_iterator() #include <cstdlib> // rand(), srand() // NOT including <algorithm> int main() { srand(time(NULL)); const int SIZE = 10; std::vector<int> vec; for(int i = 0; i < SIZE; ++i) { vec.push_back(rand() % 256); } copy(vec.begin(), vec.end(), std::ostream_iterator<int>(std::cout

问题 According to this cplusplus.com page, std::copy is in the <algorithm> header, as is std::swap and yet this works: #include <iostream> // std::cout #include <vector> // std::vector #include <iterator> // std::ostream_iterator() #include <cstdlib> // rand(), srand() // NOT including <algorithm> int main() { srand(time(NULL)); const int SIZE = 10; std::vector<int> vec; for(int i = 0; i < SIZE; ++i) { vec.push_back(rand() % 256); } copy(vec.begin(), vec.end(), std::ostream_iterator<int>(std::cout

问题 I have a simple question about using binary search in the insertion sort algorithm. More precisely, at each step of the usual insertion sort, instead of linearly comparing the element with all the elements in the previous (sorted) subarray, we just use binary search in that sorted subarray to find the place where the element belongs. I know that this reduced the number of comparisons that the algorithm makes (O(log n) instead of O(n)), but the number of swaps needed at each step still

问题 I look up online and know that list.pop() has O(1) time complexity but list.pop(i) has O(n) time complexity. While I am writing leetcode, many people use pop(i) in a for loop and they say it is O(n) time complexity and in fact it is faster than my code, which only uses one loop but many lines in that loop. I wonder why this would happen, and should I use pop(i) instead of many lines to avoid it? Example: Leetcode 26. Remove Duplicates from Sorted Array My code: (faster than 75%) class

问题 I'm reading Cormen et al., Introduction to Algorithms (3rd ed.) (PDF), section 15.4 on optimal binary search trees, but am having some trouble implementing the pseudocode for the optimal_bst function in Python. Here is the example I'm trying to apply the optimal BST to: Let us define e[i,j] as the expected cost of searching an optimal binary search tree containing the keys labeled from i to j . Ultimately, we wish to compute e[1, n] , where n is the number of keys (5 in this example). The