dictionary

问题 I need a HashMap that (1) matches keys by Object reference, and (2) maintains insertion order when iterating These functionalities are implemented in IdentityHashMap and LinkedHashMap separately. Is there any way to get a data structure that suits my need? Either one that is present in Java standard OR 3rd party libraries (like Guava), OR by using some trick on LinkedHashMap maybe, so that it uses object reference for matching keys? 回答1: You can use Guava's Equivalence for this: Equivalence

问题 I am solving a problem on LeetCode, but nobody has yet been able to explain my issue. The problem is as such: Given an arbitrary ransom note string and another string containing letters from all the magazines, write a function that will return true if the ransom note can be constructed from the magazines ; otherwise, it will return false. Each letter in the magazine string can only be used once in your ransom note. Note: You may assume that both strings contain only lowercase letters.

问题 I am solving a problem on LeetCode, but nobody has yet been able to explain my issue. The problem is as such: Given an arbitrary ransom note string and another string containing letters from all the magazines, write a function that will return true if the ransom note can be constructed from the magazines ; otherwise, it will return false. Each letter in the magazine string can only be used once in your ransom note. Note: You may assume that both strings contain only lowercase letters.

问题 I have a data frame that has as index a timestamp and a column that has list of dictionaries: index var_A 2019-08-21 09:05:49 [{"Date1": "Aug 21, 2017 9:09:51 AM","Date2": "Aug 21, 2017 9:09:54 AM","Id": "d5e665e5","num_ins": 108,"num_del": 0, "time": 356} , {"Date1": "Aug 21, 2017 9:09:57 AM","Date2": "Aug 21, 2017 9:09:59 AM","Id": "d5e665e5","num_ins": 218,"num_del": 5, "time": 166}] 2019-08-21 09:05:59 [{"Date1": "Aug 21, 2017 9:10:01 AM","Date2": "Aug 21, 2017 9:11:54 AM","Id": "d5e665e5

问题 Assume List<int> diff(List<int> a, List<int> b) { // assume same length lists List<int> diff= new List<int>(a.Count); for (int i=0; i<diff.Count; ++i) { diff[i] = a[i] - b[i]; } return diff; } I would like to have some kind of one-liner do the same, or something that uses a lambda, rather than re-writing all the boilerplate. for instance, in python, this would be either [ai-bi for ai,bi in zip(a,b)] or even np.array(a) - np.array(b) Is there a nice way to write this in C#? All my searches

问题 I'm trying to compare the identity of 2 maps package main import "fmt" func main() { a := map[int]map[int]int{1:{2:2}} b := a[1] c := a[1] // I can't do this: // if b == c // because I get: // invalid operation: b == c (map can only be compared to nil) // but as far as I can tell, mutation works, meaning that the 2 maps might actually be identical b[3] = 3 fmt.Println(c[3]) // so mutation works... fmt.Printf("b as pointer::%p\n", b) fmt.Printf("c as pointer::%p\n", c) // ok, so maybe these

问题 I'm trying to compare the identity of 2 maps package main import "fmt" func main() { a := map[int]map[int]int{1:{2:2}} b := a[1] c := a[1] // I can't do this: // if b == c // because I get: // invalid operation: b == c (map can only be compared to nil) // but as far as I can tell, mutation works, meaning that the 2 maps might actually be identical b[3] = 3 fmt.Println(c[3]) // so mutation works... fmt.Printf("b as pointer::%p\n", b) fmt.Printf("c as pointer::%p\n", c) // ok, so maybe these

问题 I'm trying to compare the identity of 2 maps package main import "fmt" func main() { a := map[int]map[int]int{1:{2:2}} b := a[1] c := a[1] // I can't do this: // if b == c // because I get: // invalid operation: b == c (map can only be compared to nil) // but as far as I can tell, mutation works, meaning that the 2 maps might actually be identical b[3] = 3 fmt.Println(c[3]) // so mutation works... fmt.Printf("b as pointer::%p\n", b) fmt.Printf("c as pointer::%p\n", c) // ok, so maybe these

问题 How can i group similar keys of a dictionary in a list if i have data = [{'quantity': 2, 'type': 'Vip'}, {'quantity': 23, 'type': 'Vip'}, {'quantity': 2, 'type': 'Regular'}, {'quantity': 2, 'type': 'Regular'}, {'quantity': 2, 'type': 'Regular'}, {'quantity': 2, 'type': 'Regular'}] and i want it to output like this res = {'Regular': [{'quantity': 2, 'type': 'Regular'},{'quantity': 2, 'type': 'Regular'},{'quantity': 2, 'type': 'Regular'}], 'Vip': [{'quantity': 23, 'type': 'Vip'},{'quantity': 23

问题 How can i group similar keys of a dictionary in a list if i have data = [{'quantity': 2, 'type': 'Vip'}, {'quantity': 23, 'type': 'Vip'}, {'quantity': 2, 'type': 'Regular'}, {'quantity': 2, 'type': 'Regular'}, {'quantity': 2, 'type': 'Regular'}, {'quantity': 2, 'type': 'Regular'}] and i want it to output like this res = {'Regular': [{'quantity': 2, 'type': 'Regular'},{'quantity': 2, 'type': 'Regular'},{'quantity': 2, 'type': 'Regular'}], 'Vip': [{'quantity': 23, 'type': 'Vip'},{'quantity': 23