#include <iostream>
#include <cstring>
#include <cstdlib>

using namespace std;

int getRightPos(char *string, char search) {
    for (int k = strlen(string); k >= 0; k--) {
        if (string[k] == search) {
            return k;
        }
    }

    return -1;
}

char *getExtension(char *path) {
    int pos = getRightPos(path, '.');

    if (pos != -1) {
        char *ext = new char[strlen(path) - pos];

        for (size_t k = 0, j = pos; k <= strlen(ext); k++, j++) {
            ext[k] = path[j];
        }

        return ext;
    }

    return nullptr;
}

char *replaceExtension(char *oldPath, char *newExt) {
    int pos = getRightPos(oldPath, '.');

    if (pos != -1) {
        const int newSize = pos + strlen(newExt) + 1;

        char *newPath = new char[newSize];

        for (int k = 0, j = 0; k < newSize; k++) {
            if (k >= pos) {
                newPath[k] = newExt[j++];
            } else {
                newPath[k] = oldPath[k];
            }
        }

        return newPath;
    }

    return oldPath;
}

int main() {
    char path[210] = "D:\\Pathname\\Superpuper\\test.ltx";

    cout << getRightPos(path, '.') << endl;
    cout << getExtension(path) << endl;
    cout << replaceExtension(path, ".jpeg");

    return 0;
}