Need help on getting the smallest three numbers on an array - c++

Question

For this program a user must enter 10 contestants and the amount of second it took for them to complete a swimming race. My problem is that I must output the 1st, 2nd and 3rd placers, so I need to get the three smallest arrays (as they would be the quickest times) but I'm unsure on how to do it. Here is my code so far.
string names[10] = {};
int times[10] = { 0 };
int num[10] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
int min1 = 0, min2 = 0, min3 = 0;
cout << "\n\n\tCrawl";
for (int i = 0; i < 10; i++)
{
cout << "\n\n\tPlease enter the name of contestant number " << num[i] << ": ";
cin >> names[i];
cout << "\n\tPlease enter the time it took for them to complete the Crawl style: ";
cin >> times[i];
while (!cin)
{
cout << "\n\tError! Please enter a valid time: ";
cin.clear();
cin.ignore();
cin >> times[i];
}
if (times[i] < times[min1])
min1 = i;
cout << "\n\n\t----------------------------------------------------------------------";
}
system("cls");
cout << "\n\n\tThe top three winners of the Crawl style race are as follows";
cout << "\n\n\t1st Place - " << names[min1];
cout << "\n\n\t2nd Place - " << names[min2];
cout << "\n\n\t3rd Place - " << names[min3];
}
_getch();
return 0;
}
As you can see, it is incomplete. I know how to get the smallest number, but its the second and third smallest that is giving me trouble.

Answer 1

your code is full of errors:
what do you do with min2 and min3 as long as you don't assign them?? they are always 0
try checking: cout << min2 << " " << min3;
also you don't initialize an array of strings like that.
why you use an array of integers for just printing number of input:
num? instead you can use i inside loop adding to it 1 each time
to solve your problem use a good way so consider using structs/clusses:
struct Athlete
{
std::string name;
int time;
};
int main()
{
Athlete theAthletes[10];
for(int i(0); i < 10; i++)
{
std::cout << "name: ";
std::getline(std::cin, theAthletes[i].name);
std::cin.sync(); // flushing the input buffer
std::cout << "time: ";
std::cin >> theAthletes[i].time;
std::cin.sync(); // flushing the input buffer
}
// sorting athletes by smaller time
for(i = 0; i < 10; i++)
for(int j(i + 1); j < 10; j++)
if(theAthletes[i].time > theAthletes[j].time)
{
Athlete tmp = theAthletes[i];
theAthletes[i] = theAthletes[j];
theAthletes[j] = tmp;
}
// printing the first three athletes
std::cout << "the first three athelets:\n\n";
std::cout << theAthletes[0].name << " : " << theAthletes[0].time << std::endl;
std::cout << theAthletes[1].name << " : " << theAthletes[1].time << std::endl;
std::cout << theAthletes[2].name << " : " << theAthletes[2].time << std::endl;
return 0;
}

Answer 2

I hope this will give u the expected output. But i suggest u to use some sorting alogirthms like bubble sort,quick sort etc.
#include <iostream>
#include<string>
using namespace std;
int main() {
int times[10] = { 0 };
int num[10] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
int min1 = 0, min2 = 0, min3 = 0,m;
string names[10] ;
cout << "\n\n\tCrawl";
for (int i = 0; i < 10; i++)
{
cout << "\n\n\tPlease enter the name of contestant number " << num[i] << ": ";
cin >> names[i];
cout << names[i];
cout << "\n\tPlease enter the time it took for them to complete the Crawl style: ";
cin >> times[i];
cout<<times[i];
while (!cin)
{
cout << "\n\tError! Please enter a valid time: ";
cin.clear();
cin.ignore();
cin >> times[i];
}
if(times[i]==times[min1]){
if(times[min1]==times[min2]){
min3=i;
}else{min2 =i;}
}else if(times[i]==times[min2]){
min3=i;
}
if (times[i] < times[min1]){
min1 = i;
cout <<i;
}
int j=0;
while(j<i){
if((times[j]>times[min1])&&(times[j]<times[min2])){
min2 =j;
j++;
}
j++;
}
m=0;
while(m<i){
if((times[m]>times[min2])&&(times[m]<times[min3])){
min3 =m;
m++;
}
m++;
}
cout << "\n\n\t----------------------------------------------------------------------";
}
cout << "\n\n\tThe top three winners of the Crawl style race are as follows";
cout << "\n\n\t1st Place - " << names[min1];
cout << "\n\n\t2nd Place - " << names[min2];
cout << "\n\n\t3rd Place - " << names[min3];
return 0;
}

Answer 3

There is actually an algorithm in the standard library that does exactly what you need: std::partial_sort. Like others have pointed out before, to use it you need to put all the participant data into a single struct, though.
So start by defining a struct that contains all relevant data. Since it seems to me that you only use the number of the contestants in order to be able to later find the name to the swimmer with the fastest time, I'd get rid of it. Of course you could also add it back in if you like.
struct Swimmer {
int time;
std::string name;
};
Since you know that there always will be exactly 10 participants in a race, you can also go ahead and replace the C-style array by a std::array.
The code to read in the users then could look like this:
std::array<Swimmer, 10> participants;
for (auto& participant : participants) {
std::cout << "\n\n\tPlease enter the name of the next contestant: ";
std::cin >> participant.name;
std::cout << "\n\tPlease enter the time it took for them to complete the Crawl style: ";
while(true) {
if (std::cin >> participant.time) {
break;
}
std::cout << "\n\tError! Please enter a valid time: ";
std::cin.clear();
std::cin.ignore();
}
std::cout << "\n\n\t----------------------------------------------------------------------";
}
Partial sorting is now essentially a one-liner:
std::partial_sort(std::begin(participants),
std::begin(participants) + 3,
std::end(participants),
[] (auto const& p1, auto const& p2) { return p1.time < p2.time; });
Finally you can simply output the names of the first three participants in the array:
std::cout << "\n\n\tThe top three winners of the Crawl style race are as follows";
std::cout << "\n\n\t1st Place - " << participants[0].name;
std::cout << "\n\n\t2nd Place - " << participants[1].name;
std::cout << "\n\n\t3rd Place - " << participants[2].name << std::endl;
The full working code can be found on coliru.

Answer 4

This is not a full solution to your problem, but just meant to point you into the right direction...
#include <iostream>
#include <limits>
#include <algorithm>
using namespace std;
template <int N>
struct RememberNsmallest {
int a[N];
RememberNsmallest() { std::fill_n(a,N,std::numeric_limits<int>::max()); }
void operator()(int x){
int smallerThan = -1;
for (int i=0;i<N;i++){
if (x < a[i]) { smallerThan = i; break;}
}
if (smallerThan == -1) return;
for (int i=N-1;i>smallerThan;i--){ a[i] = a[i-1]; }
a[smallerThan] = x;
}
};
int main() {
int a[] = { 3, 5, 123, 0 ,-123, 1000};
RememberNsmallest<3> rns;
rns = std::for_each(a,a+6,rns);
std::cout << rns.a[0] << " " << rns.a[1] << " " << rns.a[2] << std::endl;
// your code goes here
return 0;
}
This will print
-123 0 3
As you need to know also the names for the best times, you should use a
struct TimeAndName {
int time;
std::string name;
}
And change the above functor to take a TimeAndName instead of the int and make it also remember the names... or come up with a different solution ;), but in any case you should use a struct similar to TimeAndName.
As your array is rather small, you could even consider to use a std::vector<TimeAndName> and sort it via std::sort by using your custom TimeAndName::operator<.