collections

来源： https://stackoverflow.com/questions/39731980/what-is-a-simple-way-to-cache-a-list-or-other-collection-in-java

问题 In C++ we can use __gnu_pbds i.e. Policy based data structure. See the following code. #include<bits/stdc++.h> #include<ext/pb_ds/assoc_container.hpp> #include<ext/pb_ds/tree_policy.hpp> using namespace std; using namespace __gnu_pbds; typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> PBDS; int main() { PBDS st; st.insert(1); st.insert(3); st.insert(4); st.insert(10); st.insert(15); for(int i=0;i<st.size();i++) { cout<<i<<" "<< *st.find_by_order(i) <<endl

问题 In C++ we can use __gnu_pbds i.e. Policy based data structure. See the following code. #include<bits/stdc++.h> #include<ext/pb_ds/assoc_container.hpp> #include<ext/pb_ds/tree_policy.hpp> using namespace std; using namespace __gnu_pbds; typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> PBDS; int main() { PBDS st; st.insert(1); st.insert(3); st.insert(4); st.insert(10); st.insert(15); for(int i=0;i<st.size();i++) { cout<<i<<" "<< *st.find_by_order(i) <<endl

问题 I have a question for combining two linkedlist. Basically, I want to append one linkedlist to the other linkedlist. Here is my solution. Is there a more efficient way to do it without looping the first linkedlist? Any suggestion would be appreciated. static Node connect(LinkedList list1, LinkedList list2) { Node original = list1.first; Node previous = null; Node current = list1.first; while (current != null) { previous = current; current = current.next; } previous.next = list2.first; return

问题 I have a question for combining two linkedlist. Basically, I want to append one linkedlist to the other linkedlist. Here is my solution. Is there a more efficient way to do it without looping the first linkedlist? Any suggestion would be appreciated. static Node connect(LinkedList list1, LinkedList list2) { Node original = list1.first; Node previous = null; Node current = list1.first; while (current != null) { previous = current; current = current.next; } previous.next = list2.first; return

问题 I'd like to find the index of the minimum value in a C++ std::vector<double> . Here's a somewhat verbose implementation of this: //find index of smallest value in the vector int argMin(std::vector<double> vec) { std::vector<double>::iterator mins = std::min_element(vec.begin(), vec.end()); //returns all mins double min = mins[0]; //select the zeroth min if multiple mins exist for(int i=0; i < vec.size(); i++) { //Note: could use fabs( (min - vec[i]) < 0.01) if worried about floating-point

问题 I'd like to find the index of the minimum value in a C++ std::vector<double> . Here's a somewhat verbose implementation of this: //find index of smallest value in the vector int argMin(std::vector<double> vec) { std::vector<double>::iterator mins = std::min_element(vec.begin(), vec.end()); //returns all mins double min = mins[0]; //select the zeroth min if multiple mins exist for(int i=0; i < vec.size(); i++) { //Note: could use fabs( (min - vec[i]) < 0.01) if worried about floating-point

问题 Java has LinkedHashMap but there doesn't seem to be a similar solution in JavaScript. Basically, I want to be able to say var map = {}; map['a'] = 1; map['b'] = 2; Then when I iterate over the map, they are always in [{a:1}, {b:2}...] order. 回答1: I believe JavaScript Map object can help you to solve this issue: let myObject = new Map(); myObject.set('z', 33); myObject.set('1', 100); myObject.set('b', 3); for (let [key, value] of myObject) { console.log(key, value); } // z 33 // 1 100 // b 3

问题 Java has LinkedHashMap but there doesn't seem to be a similar solution in JavaScript. Basically, I want to be able to say var map = {}; map['a'] = 1; map['b'] = 2; Then when I iterate over the map, they are always in [{a:1}, {b:2}...] order. 回答1: I believe JavaScript Map object can help you to solve this issue: let myObject = new Map(); myObject.set('z', 33); myObject.set('1', 100); myObject.set('b', 3); for (let [key, value] of myObject) { console.log(key, value); } // z 33 // 1 100 // b 3

问题 Is there a dead easy way to rename a collection in mongo? Something like: db.originalCollectionName.rename('newCollectionName'); And if not, what is the best way to go about effectively renaming one? 回答1: Close. Use db.originalCollectionName.renameCollection('newCollectionName') See http://www.mongodb.org/display/DOCS/renameCollection+Command 回答2: For those who cannot rename, because the name causes an issue like: SyntaxError: Unexpected token ILLEGAL, it is because the name is illegal. You