Sorting Structs and Arrays - c++

Question

My task is to read in a file with names and scores for a game (file looks something like)
5
John Doe 200
Chris Brown 340
Chris Brown 320
John Smith 300
John Doe 600
And prints out the names in alphabetical order (last name) with the highest score from that person. So output would look something like:
Chris Brown 340
John Doe 600
John Smith 300
I figured out how to sort and print the scores from highest to lowest, but I'm lost on how to print out just the highest scores from each person... any help would be appreciated!
#include <iostream>
#include <fstream>
using namespace std;
struct playerscore
{
string first, last;
int score;
};
bool score(playerscore a, playerscore b);
void selectionsort(playerscore *A, int n);
int main()
{
string file;
int n;
cin >> file;
ifstream fin(file.c_str());
fin >> n;
// read in the names and the scores in the form of struct playerscore
playerscore *A = new playerscore[n];
for(int i = 0; i < n; i++)
fin >> A[i].first >> A[i].last >> A[i].score;
// sort the data
selectionsort(A, n);
// print in sorted order
for(int i = 0; i < n; i++)
cout << A[i].score << " ";
cout << endl;
return 0;
}
bool before(playerscore a, playerscore b)
{
return a.score > b.score;
}
void selectionsort(playerscore *A, int n)
{
for(int length = n; length > 1; length--)
{
//find imax, index of largest
int imax = 0, i;
for(i = 1; i < length; i++)
if(before(A[imax], A[i]))
imax = i;
// swap A[imax] and the last element
playerscore temp = A[imax];
A[imax] = A[length-1];
A[length-1] = temp;
}
}

Answer 1

Sort to ascending order of the name.
If the names compared are same, element with higher score should be come to earlier position of the array.
Print the first element and elements whose name differs from previous element.
Sample implementation:
#include <iostream>
#include <fstream>
using namespace std;
struct playerscore
{
string first, last;
int score;
};
bool score(playerscore a, playerscore b);
void selectionsort(playerscore *A, int n);
int main()
{
string file;
int n;
#if 0
cin >> file;
ifstream fin(file.c_str());
#else
#define fin cin // to test with online compiler
#endif
fin >> n;
// read in the names and the scores in the form of struct playerscore
playerscore *A = new playerscore[n];
for(int i = 0; i < n; i++)
fin >> A[i].first >> A[i].last >> A[i].score;
// sort the data
selectionsort(A, n);
// print in sorted order
for(int i = 0; i < n; i++)
if (i == 0 || A[i].first != A[i - 1].first || A[i].last != A[i - 1].last)
cout << A[i].first << " " << A[i].last << " " << A[i].score << "\n";
cout << endl;
return 0;
}
bool before(playerscore a, playerscore b)
{
return a.first == b.first ? (a.last == b.last ? a.score > b.score : a.last < b.last) : a.first < b.first;
}
void selectionsort(playerscore *A, int n)
{
for(int length = n; length > 1; length--)
{
//find imax, index of largest
int imax = 0, i;
for(i = 1; i < length; i++)
if(before(A[imax], A[i]))
imax = i;
// swap A[imax] and the last element
playerscore temp = A[imax];
A[imax] = A[length-1];
A[length-1] = temp;
}
}

Answer 2

You've already done the difficult part.
Suppose the ((first, last), score) pairs are already sorted, the highest score for each player is the first record for this player, so just keep the current player's name as curr_name when you visit the array:
If the next name is same as curr_name, you can safely ignore this item.
If not, print this record, and update curr_name.
The code is like blew:
#include <iostream>
#include <fstream>
#include <algorithm>
#include <vector>
#include <string>
#include <utility>
using namespace std;
bool mycmp (pair<pair<string, string>, int> a, pair<pair<string, string>, int> b) {
return a.first < b.first || (a.first == b.first && a.second > b.second);
}
int main(int argc, char *argv[])
{
ifstream fin("data.txt");
int n;
fin>>n;
vector<pair<pair<string, string>, int>> A(n);
for(int i = 0; i < n; ++i){
fin>>A[i].first.first>>A[i].first.second>>A[i].second;
}
sort(A.begin(), A.end(), mycmp);
pair<string, string> cur_name;
for(int i = 0; i < n; ++i){
if(cur_name != A[i].first){
cout<<A[i].first.first<<" "<<A[i].first.second<<" "<<A[i].second<<endl;
cur_name = A[i].first;
}
}
return 0;
}

Answer 3

As pointed out before, since it's a task I decided to rewrite the code and it should now look like this.
Sort the array based on the score
Sort the array based on alphabetical order
Print unique entries
#include <iostream>
#include <fstream>
using namespace std;
struct playerscore
{
string first, last;
int score;
};
bool score(playerscore a, playerscore b);
void selectionsort(playerscore *A, int n);
int main()
{
string file;
int n;
cin >> file;
ifstream fin(file.c_str());
fin >> n;
// read in the names and the scores in the form of struct playerscore
playerscore *A = new playerscore[n];
for (int i = 0; i < n; i++)
fin >> A[i].first >> A[i].last >> A[i].score;
// sort the data
selectionsort(A, n);
// sort alphabetically and print unique entries
for (int i=0; i<n-1; i++)
{
for (int j=i+1; j<n; j++)
{
if (A[j].last <= A[i].last && A[j].first < A[i].first)
{
playerscore tmp = A[i];
A[i] = A[j], A[j] = tmp;
}
}
playerscore max;
int j = 0;
for (int i=0; j+i<n; i++)
{
max.score = -1;
while (j+i<n && A[j+i].last == A[i].last && A[j+i].first == A[i].first)
{
if (A[j+i].score >= A[i].score)
max = A[j+i];
j++;
}
j--;
if (max.score >= 0)
cout << max.last << " " << max.first << " " << max.score << endl;
}
cout << endl;
return 0;
}
bool before(playerscore a, playerscore b)
{
return a.score > b.score;
}
void selectionsort(playerscore *A, int n)
{
for(int length = n; length > 1; length--)
{
//find imax, index of largest
int imax = 0, i;
for(i = 1; i < length; i++)
if(before(A[imax], A[i]))
imax = i;
// swap A[imax] and the last element
playerscore temp = A[imax];
A[imax] = A[length-1];
A[length-1] = temp;
}
}