hashtable

问题 Now I have this question where I was asked the cost of deleting a value from a hash table when we used linear probing while the insertion process. What I could figure out from reading various stuff on the internet is that it has to do something with the load factor. Though I am not sure, but I read a relation between the load factor and no of probes required and it is No of probes = 1 / (1-LF). So I believe the cost has to be dependent on the probe sequence. But then another thought ruins

问题 I just had a homework assignment that wanted me to add all the Java keywords to a HashSet. Then read in a .java file, and count how many times any keyword appeared in the .java file. The route I took was: Created an String[] array that contained all the keywords. Created a HashSet, and used Collections.addAll to add the array to the HashSet. Then as I iterated through the text file I would check it by HashSet.contains(currentWordFromFile); Someone recommended using a HashTable to do this.

问题 I'm currently working on a game, where I need to create a transposition table for my AI. I implemented Hashtable so that the key to the Hashtable is a state under consideration and its corresponding value is the optimal next move. However, when I save the Hashtable in Android's internal storage and restore it next time, it seems to have some saved data, but the keys (i.e. game states) are different than the keys I have saved in the previous instance. Here is how I save and restore my data:

问题 The hashCode of a java Hashtable element is always unique? If not, how can I guarantee that one search will give me the right element? 回答1: Not necessarily. Two distinct (and not-equal) objects can have the same hashcode. 回答2: First thing first. You should consider to use HashMap instead of Hashtable, as the latter is considered obsolete (it enforces implicit synchronization, which is not required most of the time. If you need a synchronized HashMap, it is easily doable) Now, regarding your

问题 I can't seem to get my splatting to work in my Invoke-WmiMethod command. I declare the hash table like so: $HKU = 2147483651 $MyParams = @{ 'Class' = 'StdRegProv'; 'Name' = 'EnumKey'; 'ArgumentList' = "$HKU,''"; 'ComputerName' = ''; } # additional code determining ComputerName... # $MyParams['ComputerName'] = $MyComputer; $Vals = Invoke-WmiMethod @MyParams This line gives me the following error: Invoke-WmiMethod : Input string was not in a correct format. At C:\Users\Person\Desktop\tmp.ps1

问题 While having a look inside HashMap class, I came across this method :- /** * This method is invoked whenever the value in an entry is * overwritten by an invocation of put(k,v) for a key k that's already * in the HashMap. */ void recordAccess(HashMap<K,V> m) { } Actually, this method is defined inside the inner class of Entry<K, V> I'm not able to make out of that comment. What does this method do ? PS : I can also see this method being called inside's HashMap's putForNullKey() method private

问题 The problem statement is as follows: The goal of this problem is to implement a variant of the 2-SUM algorithm. The file contains 1 million integers, both positive and negative (there might be some repetitions!).This is your array of integers, with the ith row of the file specifying the ith entry of the array. Your task is to compute the number of target values t in the interval [-10000,10000] (inclusive) such that there are distinct numbers x,y in the input file that satisfy x+y=t. Write

问题 Does anyone know why the java jdk implementation of hashtable does not rehash the table upon remove ? What if space usage is too low? Isnt it a reason to reduce size and rehash? Just like load factor 0.75 which triggers rehash on put, we could have a lower bound like 0.25 (of course analysis can be done on the best value here) on the density of the table and trigger the rehash again, provided the size of the table is greater than the initialCapacity. 回答1: Rehashing is an expensive operation

问题 I'm reading the Hashtable's code. and I am confused about the toString() method, the code is like this : public synchronized String toString() { int max = size() - 1; if (max == -1) return "{}"; StringBuilder sb = new StringBuilder(); Iterator<Map.Entry<K,V>> it = entrySet().iterator(); sb.append('{'); for (int i = 0; ; i++) { Map.Entry<K,V> e = it.next(); K key = e.getKey(); V value = e.getValue(); // Is "key == this" possible ? What the "this" stands for ? sb.append(key == this ? "(this Map

问题 I have the following dictionary. var = a = { 'Black': { 'grams': 1906, 'price': 2.05}, 'Blue': { 'grams': 9526, 'price': 22.88}, 'Gold': { 'grams': 194, 'price': 8.24}, 'Magenta': { 'grams': 6035, 'price': 56.69}, 'Maroon': { 'grams': 922, 'price': 18.76}, 'Mint green': { 'grams': 9961, 'price': 63.89}, 'Orchid': { 'grams': 4970, 'price': 10.78}, 'Tan': { 'grams': 6738, 'price': 50.54}, 'Yellow': { 'grams': 6045, 'price': 54.19} } How can I sort it based on the price . So the resulting