C++ Counting occurrences using MAP (STL)
Counting occurrences
We may be doing many projects where there is a need for making count of occurrences. By using the map in STL library we can make count of different characters or values in a string or stream. It is just like using the dictionary in python.
We have map and unordered_map. map is a self balancing BST, while unordered_map is a hash table. Both these internal structures have their own pros and cons, so you have to choose which you want depending on the data you have
EXAMPLE:
#include <iostream>
#include <map>
#include <unordered_map>
using namespace std;
int main()
{
string str = "cppsecrets is the best website for learning c++";
// unordered_map<char, int> counter; // This is unordered_map
map<char, int> counter;
for (char i : str)
if (i != ' ') // Counts all charachters other than white spaces.
counter[i]++;
for (auto i : counter)
cout << i.first << " : " << i.second << "\n"; // Accessing map elements
return 0;
}
OUTPUT:
+ : 2
a : 1
b : 2
c : 3
e : 7
f : 1
g : 1
h : 1
i : 3
l : 1
n : 2
o : 1
p : 2
r : 3
s : 5
t : 4
w : 1
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