gistfile1.txt

#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <numeric>
#include <unordered_map>

int main() {
    std::vector<std::vector<int>> matrix = {{1,2,3},{4,5,6},{7,8,9}};
    int evenCount2D = std::accumulate(matrix.begin(), matrix.end(), 0,
        [](int acc, const std::vector<int>& row) {
            return acc + std::count_if(row.begin(), row.end(),
                [](int x){ return x % 2 == 0; });
        });
    std::cout << evenCount2D << std::endl;

    std::vector<int> v = {1,2,3,4,5,6};
    std::vector<int> evens;
    std::copy_if(v.begin(), v.end(), std::back_inserter(evens),
        [](int x){ return x % 2 == 0; });
    for(int x : evens) std::cout << x << " ";
    std::cout << std::endl;

    v.erase(std::remove_if(v.begin(), v.end(),
        [](int x){ return x < 0; }), v.end());
    for(int x : v) std::cout << x << " ";
    std::cout << std::endl;

    std::vector<std::string> words = {"meet","sea","son","night"};
    char c = 's';
    int countByChar = std::count_if(words.begin(), words.end(),
        [c](const std::string& s){
            return !s.empty() && s[0] == c;
        });
    std::cout << countByChar << std::endl;

    std::unordered_map<char,int> result;
    std::for_each(words.begin(), words.end(),
        [&result](const std::string& s){
            if(!s.empty()) result[s[0]]++;
        });
    for(const auto& [k,v] : result)
        std::cout << k << " - " << v << std::endl;
}

с++