Selection sort not grabbing last element in array - c++

Question

void ProcessSort(int studentIDs[], string studentNames[], int num)
{
for (int i = 0; i < num - 1; i++)
{
int mindex = 0;
//DO6: finish the inner loop
// Hint: it should start from i+1 and go until num-1
// if studentNames[j] is greater than studentNames[mindex]
// then store j in mindex
for (int j = i+1; j < num - 1; j++) {
if (studentNames[mindex] < studentNames[j]) {
mindex = j;
}
}
//DO7: Swap student names
SwapNames(studentNames[mindex], studentNames[i]);
//DO8: Swap student IDs'
SwapIDs(studentIDs[mindex], studentIDs[i]);
}
cout << "Class List sorted by name." << endl;
}
Selection sort seems not to grab last element in array. There are two parallel arrays, one with names and one with ids, but it seems to be that the last name in the student names array isnt registered with the sort. Any help would be greatly appreciated.

Answer 1

The body of the outer loop should look at least like
int mindex = i;
//DO6: finish the inner loop
// Hint: it should start from i+1 and go until num-1
// if studentNames[j] is greater than studentNames[mindex]
// then store j in mindex
for (int j = i+1; j < num; j++) {
if (studentNames[mindex] < studentNames[j]) {
mindex = j;
}
}
This condition
if (studentNames[mindex] < studentNames[j]) {
provides sorting in the descending order.
Here is a demonstrative program.
#include <iostream>
#include <string>
#include <utility>
void ProcessSort( int studentIDs[], std::string studentNames[], size_t n )
{
for ( size_t i = 0; i < n; i++)
{
size_t mindex = i;
//DO6: finish the inner loop
// Hint: it should start from i+1 and go until num-1
// if studentNames[j] is greater than studentNames[mindex]
// then store j in mindex
for ( size_t j = i + 1; j < n; j++ )
{
if ( studentNames[mindex] < studentNames[j] ) mindex = j;
}
//DO7: Swap student names
if ( i != mindex )
{
std::swap( studentNames[mindex], studentNames[i] );
//DO8: Swap student IDs'
std::swap( studentIDs[mindex], studentIDs[i] );
}
}
}
int main()
{
int studentIDs[] = { 495, 520, 550, 666 };
std::string studentNames[] = { "Kyle", "Liam", "Bill", "Michael" };
const size_t N = sizeof( studentIDs ) / sizeof( *studentIDs );
for ( size_t i = 0; i < N; i++ )
{
std::cout << "( " << studentNames[i] << ", " << studentIDs[i] << " ) ";
}
std::cout << std::endl;
ProcessSort( studentIDs, studentNames, N );
for ( size_t i = 0; i < N; i++ )
{
std::cout << "( " << studentNames[i] << ", " << studentIDs[i] << " ) ";
}
std::cout << std::endl;
return 0;
}
Its output is
( Kyle, 495 ) ( Liam, 520 ) ( Bill, 550 ) ( Michael, 666 )
( Michael, 666 ) ( Liam, 520 ) ( Kyle, 495 ) ( Bill, 550 )