I have a vector of structures to hold student records:
struct record {
int id;
string name;
string address;
double gpa;
int *scorePtr;
};
I'm trying sort the vector by id but I can't seem to figure it out. I read the values into the vector from a .txt file, but when I try to sort it, none of the elements are swapped.
below are my functions for the quick sort:
void quickSort(vector<record> set, int start, int end) {
int pivotPoint;
if (start < end) {
//get the pivot point
pivotPoint = partition(set, start, end);
//sort first sublist
quickSort(set, start, pivotPoint - 1);
//sort second sublist
quickSort(set, pivotPoint + 1, end);
}
}
int partition(vector<record> set, int start, int end) {
int pivotValue, pivotIndex, mid;
mid = (start + end) / 2;
swapInt(set[start].id, set[mid].id);
swapString(set[start].name, set[mid].name);
swapString(set[start].address, set[mid].address);
swapDouble(set[start].gpa, set[mid].gpa);
pivotIndex = start;
pivotValue = set[start].id;
for(int scan = start + 1; scan <= end; scan++) {
if (set[scan].id < pivotValue) {
pivotIndex++;
swapInt(set[pivotIndex].id, set[scan].id);
swapString(set[pivotIndex].name, set[scan].name);
swapString(set[pivotIndex].address, set[scan].address);
swapDouble(set[pivotIndex].gpa, set[scan].gpa);
}
}
swapInt(set[start].id, set[pivotIndex].id);
swapString(set[start].name, set[pivotIndex].name);
swapString(set[start].address, set[pivotIndex].address);
swapDouble(set[start].gpa, set[pivotIndex].gpa);
return pivotIndex;
}
void swapInt(int &value1, int &value2) {
int temp = value1;
value1 = value2;
value2 = temp;
}
void swapString(string &value1, string &value2) {
string temp = value1;
value1 = value2;
value2 = temp;
}
void swapDouble(double &value1, double &value2) {
double temp = value1;
value1 = value2;
value2 = temp;
}
And the loops in main() for displaying the vector:
//output vector
for(int k = 0; k < 20; k++) {
cout << sub[k].id << endl << sub[k].name << endl;
cout << sub[k].address << endl << fixed << setprecision(1) << sub[k].gpa << endl;
}
quickSort(sub, 0, 19);
cout << endl << endl;
//output vector
for(int k = 0; k < 20; k++) {
cout << sub[k].id << endl << sub[k].name << endl;
cout << sub[k].address << endl << fixed << setprecision(1) << sub[k].gpa << endl;
}
When I run it I just get the same list twice, unsorted. Any help is appreciated!
you can simply use the std::sort
function to sort the vector:
bool comp(record rl, record rr) {
return (rl.id < rr.id);
}
vector<record> v;
std::sort(v.begin(), v.end(), comp);
As Slava pointed out in the comments, I needed to pass the vector by reference to my functions. Before I was just editing a local copy of the vector.
void quickSort(vector<record> &set, int start, int end) {
int partition(vector<record> &set, int start, int end) {
Thanks Slava!
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