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#include <string>
#include <iostream>
#include <sstream>
#include <vector>
#include <cctype>
#include <algorithm>

using std::stringstream;
using std::string;
using std::cout;
using std::endl;
using std::vector;
using std::tolower;
using std::transform;

#define PRINT(X) cout << (#X) << " = " << X << endl

// transforms a string to lowercase
// exists in popular libraries such as "boost"
string str_tolower(string s) {
    // This is a "lambda".
    // Interface fix because standard library `tolower` has a weird type.
    auto my_tolower = [](unsigned char c){ return tolower(c); };
    transform(s.begin(), s.end(), s.begin(), my_tolower);
    return s;
}

int search(string target, vector<string> const& lst) {
    target = str_tolower(target);
    // Lambda to check whether a string is the target
    auto is_target = [&](string s) {
        return target == str_tolower(s);
    };
    // Standard library function that searches a vector
    auto it = find_if(lst.begin(), lst.end(), is_target);
    // If not found
    if(it == lst.end())
        return -1;
    // If found, compute and return index
    return it - lst.begin();
}

int main() {
    vector<string> v {"Aaa", "Bbb", "Ccc"};
    PRINT(search("BBB", v)); // 1
    PRINT(search("DDD", v)); // not found: -1
    PRINT(search("aaa", v)); // 0
    return 0;
}