#include <algorithm>
#include <cassert>
#include <initializer_list>
#include <iostream>
#include <map>

template<typename Key, typename Value>
bool HasDuplicates(const std::map<Key, Value> &bimap) {
  // Create a map to use the values as keys
  std::map<Value, Key> value_key_map;
  for (auto &kvp : bimap) value_key_map.emplace(kvp.second, kvp.first);

  // If there are no duplicate values then the sizes should be the same
  std::cout << "HasDuplicates: " << std::boolalpha << (value_key_map.size() != bimap.size()) << std::endl;
  return (value_key_map.size() != bimap.size());
}

template<typename Key, typename Value>
class BiMap {
 public:
  explicit BiMap(std::initializer_list<std::pair<Key, Value>> &&items) : bimap_{items.begin(), items.end()} {
    assert(!HasDuplicates(bimap_));
  }

  Key GetKeyFromValue(const Value &value) const {
    auto it = std::find_if(bimap_.begin(), bimap_.end(), [&value](const std::pair<Key, Value> &kvp) {
      return kvp.second == value;
    });
    return (it != bimap_.end() ? it->first : Key());
  }

  Value GetValueFromKey(const Key &key) const {
    auto it = bimap_.find(key);
    return (it != bimap_.end() ? it->second : Value());
  }

 private:
  const std::map<Key, Value> bimap_;
};

int main(int argc, char *argv[]) {
  // Test 1: No duplicates
  std::cout << "**No duplicates test:**" << std::endl;
  const BiMap<std::string, int> bi_map_no_dups({{"foo", 1}, {"bar", 2}, {"foobar", 3}});
  std::cout << "foo: " << bi_map_no_dups.GetValueFromKey("foo") << std::endl;
  std::cout << "bar: " << bi_map_no_dups.GetValueFromKey("bar") << std::endl;
  std::cout << "foobar: " << bi_map_no_dups.GetValueFromKey("foobar") << std::endl;

  // Test 2: Duplicates
  std::cout << "**Duplicates test:**" << std::endl;
  const BiMap<std::string, int> bi_map_dups({{"foo", 1}, {"bar", 2}, {"foobar", 1}});
  std::cout << "foo: " << bi_map_dups.GetValueFromKey("foo") << std::endl;
  std::cout << "bar: " << bi_map_dups.GetValueFromKey("bar") << std::endl;
  std::cout << "foobar: " << bi_map_dups.GetValueFromKey("foobar") << std::endl;

  return 0;
}
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Read inputs from stdin

OneCompiler's C++ online compiler supports stdin and users can give inputs to programs using the STDIN textbox under the I/O tab. Following is a sample program which takes name as input and print your name with hello.

#include <iostream>
#include <string>
using namespace std;

int main() 
{
    string name;
    cout << "Enter name:";
    getline (cin, name);
    cout << "Hello " << name;
    return 0;
}

About C++

C++ is a widely used middle-level programming language.

  • Supports different platforms like Windows, various Linux flavours, MacOS etc
  • C++ supports OOPS concepts like Inheritance, Polymorphism, Encapsulation and Abstraction.
  • Case-sensitive
  • C++ is a compiler based language
  • C++ supports structured programming language
  • C++ provides alot of inbuilt functions and also supports dynamic memory allocation.
  • Like C, C++ also allows you to play with memory using Pointers.

Syntax help

Loops

1. If-Else:

When ever you want to perform a set of operations based on a condition If-Else is used.

if(conditional-expression) {
   //code
}
else {
   //code
}

You can also use if-else for nested Ifs and If-Else-If ladder when multiple conditions are to be performed on a single variable.

2. Switch:

Switch is an alternative to If-Else-If ladder.

switch(conditional-expression){    
case value1:    
 // code    
 break;  // optional  
case value2:    
 // code    
 break;  // optional  
......    
    
default:     
 code to be executed when all the above cases are not matched;    
}

3. For:

For loop is used to iterate a set of statements based on a condition.

for(Initialization; Condition; Increment/decrement){  
  //code  
}

4. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while (condition) {  
// code 
}

5. Do-While:

Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.

do {  
 // code 
} while (condition);

Functions

Function is a sub-routine which contains set of statements. Usually functions are written when multiple calls are required to same set of statements which increases re-usuability and modularity. Function gets run only when it is called.

How to declare a Function:

return_type function_name(parameters);

How to call a Function:

function_name (parameters)

How to define a Function:

return_type function_name(parameters) {  
 // code
}