Answer to Question #209117 in C++ for tumi

Question

Write a program that determines the frequency of each char in an input le. Your program

should

• read in an unknown number of chars from an input le named input.txt,

• using a function written by you, determine the frequency of occurrence of each char in

the list

• write each char followed by the frequency to the output le output.txt.

• The chars should appear in the output le in the same order as they rst appeared in

the input le.

First draw a 

ow chart and then attempt the code.

Example 1

Example input and output les can be seen in Listings 9 and 10.

Listing 9: Example of input.txt

1 a

2 a

3 f

4 e

5 v

6 x

7 a

8 v

9 f

10 f

11 f

12 g

Page 4 of 5

Listing 10: Example of output.txt

1 a 3

2 f 4

3 e 1

4 v 2

5 x 1

6 g 1

Example 2

Example of additional input and output les can be seen in Listings 11 and 12.

Listing 11: Example of input.txt

1 a

2 b

3 a

4 b

5 a

6 b

7 b

Listing 12: Example of output.txt

1 a 3

2 b 4

Answer 1

#include <fstream>
#include <cctype>
using namespace std;


int main() {
    char appearedCh[26];
    int frequency[26];
    int numCh = 0;
    char ch;


    ifstream ifs("input.txt");
    while ( (ifs >> ch)) {
        ch = tolower(ch);
        if ( ch < 'a' || ch > 'z') {
            continue;
        }

        int i;
        for (i=0; i<numCh; ++i) {
            if (appearedCh[i] == ch) {
                break;
            }
        }
        if (i == numCh) {
            appearedCh[i] = ch;
            frequency[i] = 1;
            numCh++;
        }
        else {
            frequency[i]++;
        }
    }
    ifs.close();

    ofstream ofs("output.txt");
    for (int i=0; i<numCh; ++i) {
        ofs << appearedCh[i] << " " << frequency[i] << endl;
    }
    ofs.close();
}