unordered-map

问题 I constructed an unordered_map using key type rot3d, which is defined below: #ifndef EPS6 #define EPS6 1.0e-6 #endif struct rot3d { double agl[3]; // alpha, beta, gamma in ascending order bool operator==(const rot3d &other) const { // printf("== used\n"); return abs(agl[0]-other.agl[0]) <= EPS6 && abs(agl[1]-other.agl[1]) <= EPS6 && abs(agl[2]-other.agl[2]) <= EPS6; } }; Equality of rot3d is defined by the condition that each component is within a small range of the same component from the

问题 I constructed an unordered_map using key type rot3d, which is defined below: #ifndef EPS6 #define EPS6 1.0e-6 #endif struct rot3d { double agl[3]; // alpha, beta, gamma in ascending order bool operator==(const rot3d &other) const { // printf("== used\n"); return abs(agl[0]-other.agl[0]) <= EPS6 && abs(agl[1]-other.agl[1]) <= EPS6 && abs(agl[2]-other.agl[2]) <= EPS6; } }; Equality of rot3d is defined by the condition that each component is within a small range of the same component from the

问题 This question already has an answer here : C++11 get all items of one bucket in a unordered_map (1 answer) Closed 5 years ago . for std::unordered_map , can you access the elements in some bucket i if its bucket_size is not zero? 回答1: The answer is to use std::unordered_map::begin(bucket_num) or std::unordered_map::cbegin(bucket_num) to get the iterator pointing to the the first element to that bucket and iterate to the end of the bucket std::unordered_map::end(bucket_num) for ( auto it = u

问题 This question already has an answer here : C++11 get all items of one bucket in a unordered_map (1 answer) Closed 5 years ago . for std::unordered_map , can you access the elements in some bucket i if its bucket_size is not zero? 回答1: The answer is to use std::unordered_map::begin(bucket_num) or std::unordered_map::cbegin(bucket_num) to get the iterator pointing to the the first element to that bucket and iterate to the end of the bucket std::unordered_map::end(bucket_num) for ( auto it = u

问题 #include <iostream> #include <unordered_map> #include <string> struct tree_node { // tree_node() : attrib_val{"null"} {} std::unordered_map<std::string, tree_node> child; }; int main(int argc, char const *argv[]) { return 0; } This code compiles just fine on my mac with clang: $ g++ --version Configured with: --prefix=/Library/Developer/CommandLineTools/usr --with-gxx-include-dir=/Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk/usr/include/c++/4.2.1 Apple LLVM version 10.0.1 (clang

问题 #include <iostream> #include <unordered_map> #include <string> struct tree_node { // tree_node() : attrib_val{"null"} {} std::unordered_map<std::string, tree_node> child; }; int main(int argc, char const *argv[]) { return 0; } This code compiles just fine on my mac with clang: $ g++ --version Configured with: --prefix=/Library/Developer/CommandLineTools/usr --with-gxx-include-dir=/Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk/usr/include/c++/4.2.1 Apple LLVM version 10.0.1 (clang

问题 In other words, if I fill two unordered_map , or unordered_set , objects with exactly the same content and the same hashing function, will iterating over them give the same sequence of key/value pairs? If so, then what are the conditions for this to hold (e.g. same hashing function, same keys, not necessarily same values). 回答1: No. There is no requirement, for example, that objects that have the same hash be placed in any particular order. In fact, in general it's impossible for an unordered

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 was curious on vector lookup vs map lookup and wrote a little test program for it.. its seems like vector is always faster the way I'm using it.. is there something else I should take into consideration here? Is the test biased in any way? The results of a run is at the bottom.. its in nanoseconds, but gcc doesn't seem to support it on my platform. Using string for the lookup would of course change things a lot. The compile line I'm using is this: g++ -O3 --std=c++0x -o lookup lookup.cpp