检查键是否存在于C++映射或unordered_map中

C++映射和unordered_map初始化为一些键及其各自的映射值。
例子：

Input : 
Map : 1 -> 4, 2 -> 6, 4 -> 6
Check1 : 5, Check2 : 4
Output : 5 : Not present, 4 : Present

C++实现：

map

// CPP code to check if a
// key is present in a map
#include 
using namespace std;
  
// Function to check if the key is present or not
string check_key(map m, int key)
{
    // Key is not present
    if (m.find(key) == m.end())
        return "Not Present";
  
    return "Present";
}
  
// Driver
int main()
{
    map m;
  
    // Initializing keys and mapped values
    m[1] = 4;
    m[2] = 6;
    m[4] = 6;
  
    // Keys to be checked
    int check1 = 5, check2 = 4;
  
    // Function call
    cout << check1 << ": " << check_key(m, check1) << '\n';
    cout << check2 << ": " << check_key(m, check2);
}

unordered_map

// CPP code to check if a key is present 
// in an unordered_map
#include 
using namespace std;
  
// Function to check if the key is present or not
string check_key(unordered_map m, int key)
{
    // Key is not present
    if (m.find(key) == m.end())
        return "Not Present";
  
    return "Present";
}
  
// Driver
int main()
{
    unordered_map m;
  
    // Initialising keys and mapped values
    m[1] = 4;
    m[2] = 6;
    m[4] = 6;
  
    // Keys to be checked
    int check1 = 5, check2 = 4;
  
    // Function call
    cout << check1 << ": " << check_key(m, check1) << '\n';
    cout << check2 << ": " << check_key(m, check2);
}

输出：

5: Not Present
4: Present

要从最佳影片策划和实践问题去学习，检查了C++基础课程为基础，以先进的C++和C++ STL课程基础加上STL。要完成从学习语言到DS Algo等的更多准备工作，请参阅“完整面试准备课程” 。