comparator

问题 This is the code: struct comp { bool operator()(Reputation *one, Reputation *two) { if (one->Amount < 0 && two->Amount >= 0) return false; if (one->Amount >= 0 && two->Amount < 0) return true; if (one->Amount >= 0) return one->Amount <= two->Amount; else return one->Amount >= two->Amount; } }; And this is the problem: Debug Assertion Failed! File: ..\VC\include\xtree Line: 638 Expression: invalid operator< After that, I can choose "Abort", "Retry" or "Ignore". If I choose ignore many more

问题 I came across some java code for doing a prefix search on a JList. Looking at it however, the meat of the algorithm is quite inefficient, using a linear search over the list for each keypress, and doing a slow case conversion within the tight loop. I would imagine for very large amounts of data, a custom-implemented ternary search tree would be a much more efficient solution. However, if one was striving for simple code and did not have the performance requirements necessitating such

问题 I have an n*2 sized array. I want to sort them using qsort based on their value of the 2nd column. #include<stdio.h> int cmp(const int **a, const int **b) { //return 0; //return *a[1] - *b[1] // return *a - *b; } int main() { int t; // test cases scanf("%d", &t); for(int i=0; i<t; i++) { int n; scanf("%d", &n); // size of array int **arr = (int **)malloc(n * sizeof(int *)); for(int j =0; j< n; j++) { arr[j] = (int *) malloc(2*sizeof(int)); } for(int j =0; j< 2; j++) { for(int k =0; k< n; k++)

问题 How can I set a custom comparator for a specific column in JTable? The third column of my table contains String representaion of double values and I want to creat a comparator for that column so that when I click on the header of that column it will sort according to that comparator. 回答1: The first question is why, if you are managing doubles, you are dealing with Strings. It should be better if you used the doubles and just set the format in the CellRenderer for that column. Anyway, what you

问题 I have created an implementation of Comparator<Entity> , but when I use this comparator to sort an Array<Entity> . I will receive an java.lang.NullPointerException , because when I map the entity to a static collections which is already removed. Now my problem is I don't know what to return to skip the compare method. public class CustomComparator implements Comparator<Entity> { public int compare(Entity e1, Entity e2) { if( e1== null || e2 == null) { return // don't know what to return to

问题 I want to add a condition that also sorts according to the DATE (desc order) of the item.startReading. item.startReading value has the date value in the string format 2018-10-20T12:05:41 . But I have no clue how to add this logic to the current code. Before the user clicks the magazine or the book item, the value of item.startReading is null . . When the user clicks the either one of the items, I want the newest item.startReading to go to the top like the following. Sorry for my explanation,

问题 File is like this: name1 134.2 name2 456.7 name3 265.3 ... ... I read the text file and store in HashMap after that I want to sort in order(by the highest value) but the problem is that because I sort the values in String, I cant compare it. So..is there a way to put the values of textfile into hashmap in double or integer form? import java.io.*; import java.util.*; class Test { public static void main(String[] args) throws FileNotFoundException { Scanner scanner = new Scanner(new FileReader(

问题 I have a Map with an enumeration type as the key and Double as the value. I want to sort this based on the Double values. So I got the entry set and want to use Collections.sort() with a comparator. I have the following code for the comparator class ScoreComparator<Map.Entry<K, V>> implements Comparator<Map.Entry<K, V>> { public int compare(Map.Entry<K, V> o1, Map.Entry<K, V> o2) { return o1.getValue().compareTo(o2.getValue()); } } I am getting the following error messages Syntax error on

问题 I am developing a small application , I have an "Employee" class with methods and corresponding attributes (name , salary , date .. ) and another class that is a list of employees , which I use an arraylist to store employees and different methods , such as adding employee , delete employee . Now I 'm trying to sort employees by alphabetical order and date of hire (lowest to highest). But I have a little problem, I can not use the method compare more than 2 times, I have been researching and

问题 This question already has answers here : Sorting Java objects using multiple keys (7 answers) Sort a Map<Key, Value> by values (54 answers) Closed 5 months ago . I am creating a word frequency program which works good with counting the words. I am using a hashmap to store the word frequencies. I use the word as the key and the count as the value. However, I want to sort the hashMap at the end first by the word frequency and then by key alphabetically like this: it - 2 of - 2 the - 2 times- 2