Make dynamically allocated object type string - c++

Question

I need to make dynamically allocated object type of string to store sentences and after that sentences should be sorted in alphabetical order using std::sort.
This would be correct solution using char array:
#include <cstring>
#include <iostream>
#include <new>
#include <string>
#include <algorithm>
int main() {
std::cout << "How many senteces: ";
int n;
std::cin >> n;
std::cin.ignore(1000, '\n');
char ** sentence = nullptr;
std::cout << "Enter senteces:" << std::endl;
try {
sentence = new char * [n];
for (int i = 0; i < n; i++)
sentence[i] = nullptr;
for (int i = 0; i < n; i++) {
char temp[1000];
std::cin.getline(temp, 1000);
sentence[i] = new char[strlen(temp) + 1];
strcpy(sentence[i], temp);
}
std::sort(sentence, sentence + n, [](const char * a,
const char * b) {
return std::strcmp(a, b) < 0;
});
std::cout << "Sorted sentences:" << std::endl;
for (int i = 0; i < n; i++)
std::cout << sentence[i] << std::endl;
for (int i = 0; i < n; i++)
delete[] sentence[i];
delete[] sentence;
} catch (...) {
std::cout << "Problems with memory!";
return 0;
}
return 0;
}
When I try to convert this to dynamically allocated array type of string, like this:
#include <cstring>
#include <iostream>
#include <new>
#include <string>
#include <algorithm>
#include <cctype>
int main() {
std::cout << "How many senteces: ";
int n;
std::cin >> n;
std::cin.ignore(1000, '\n');
std::string ** sentence = nullptr;
std::cout << "Enter senteces:" << std::endl;
try {
sentence = new std::string * [n];
for (int i = 0; i < n; i++)
sentence[i] = nullptr;
for (int i = 0; i < n; i++) {
std::string temp;
std::getline(std::cin, temp);
sentence[i] = new std::string[temp.length() + 1];
temp = sentence[i];
}
std::sort(sentence, sentence + n, [](std::string a,
std::string b) {
for (char & c: a) c = std::toupper(c);
for (char & c: b) c = std::toupper(c);
return a < b;
});
std::cout << "Sorted sentences:" << std::endl;
for (int i = 0; i < n; i++)
std::cout << sentence[i] << std::endl;
for (int i = 0; i < n; i++)
delete[] sentence[i];
delete[] sentence;
} catch (...) {
std::cout << "Problems with memory!";
return 0;
}
return 0;
}
I get a bunch of errors. Could you explain me how to convert this program of dynamically allocation of char array to dynamically allocated string array on a correct way?

Answer 1

It looks like you think std::string "corresponds to" char, but it corresponds to char*.
You want std::string* sentence = nullptr;.
(A lot of the point of this exercise is to notice how much easier it gets when you don't need to allocate the strings yourself.)
int main() {
try {
std::cout << "How many sentences: ";
int n;
std::cin >> n;
std::cin.ignore(1000, '\n');
std::cout << "Enter sentences:" << std::endl;
std::string* sentence = new std::string [n];
for (int i = 0; i < n; i++) {
std::getline(std::cin, sentence[i]);
}
std::sort(sentence, sentence + n, [](std::string a,
std::string b) {
for (char & c: a) c = std::toupper(c);
for (char & c: b) c = std::toupper(c);
return a < b;
});
std::cout << "Sorted sentences:" << std::endl;
for (int i = 0; i < n; i++)
std::cout << sentence[i] << std::endl;
delete[] sentence;
} catch (...) {
std::cout << "Problems with memory!";
}
}