How to create dynamic 2D array of different size strings

I want to read a .txt file.

.txt file will have N-rows and M-cols.

Each word present in the txt file will have varying length.

Sample txt file:

Suppose N = 4 rows

Suppose M = 5 cols

content of txt file:

aa bbb cc dddddddd eeee

aa bbbbbbbbbbbb cc ddddddddddd eeee

aaaaaaaaaa bb cc d e

a b c d eeee

What I have to do:

I have to store these strings into a 2D array of strings such that it looks like this:

arr[4][5] =  

[aa             bbb              cc     dddddddd        eeee]

[aa             bbbbbbbbbbbb     cc     ddddddddddd     eeee]

[aaaaaaaaaa     bb               cc     d               e   ]

[a              b                c      d               eeee]

I know how to create dynamic 2D array of integer and its working fine:

int** arr;
int* temp;

arr = (int**)malloc(row*sizeof(int*));
temp = (int*)malloc(row * col * sizeof(int));
for (int i = 0; i < row; i++)
{
    arr[i] = temp + (i * col);
}
int count = 0;
//setting values in 2-D array
for (int i = 0; i < row; i++)
{
    for (int j = 0; j < col; j++)
    {
        arr[i][j] = count++;
    }
}

But, when I am trying to do the same thing for strings, its crashing.

string** arr;
string* temp;

arr = (string**)malloc(row*sizeof(string*));
temp = (string*)malloc(row * col * sizeof(string));
for (int i = 0; i < row; i++)
{
    arr[i] = temp + (i * col);
}

//setting values in 2-D array
for (int i = 0; i < row; i++)
{
    for (int j = 0; j < col; j++)
    {
        arr[i][j].append("hello"); // CRASH here !!
    }
}

How to store each words in an array??