Algorithm STL/QUIZ/5

#1

Please Share proof of compartor function that how it works for better understanding such that we can iterate over it and can easily write our own comparator

#2

@lakshaywadhwa001 hey,we can write our own comparator function and pass it as a third parameter in sort functiom.This “comparator” function returns a value; convertible to bool, which basically tells us whether the passed “first” argument should be placed before the passed “second” argument or not.
For eg: In the code below, suppose intervals {6,8} and {1,9} are passed as arguments in the “compareInterval” function(comparator function). Now as i1.first (=6) > i2.first (=1), so our function returns “false”, which tells us that “first” argument should not be placed before “second” argument and so sorting will be done in order like {1,9} first and then {6,8} as next.

// A C++ program to demonstrate STL sort() using
// our own comparator
#include<bits/stdc++.h>
using namespace std;

// An interval has a start time and end time
struct Interval
{
int start, end;
};

// Compares two intervals according to staring times.
bool compareInterval(Interval i1, Interval i2)
{
return (i1.start < i2.start);
}

int main()
{
Interval arr[] = { {6,8}, {1,9}, {2,4}, {4,7} };
int n = sizeof(arr)/sizeof(arr[0]);

// sort the intervals in increasing order of 
// start time 
sort(arr, arr+n, compareInterval); 

cout << "Intervals sorted by start time : \n"; 
for (int i=0; i<n; i++) 
   cout << "[" << arr[i].start << "," << arr[i].end 
        << "] "; 

return 0;

}
Output:
Intervals sorted by start time :
[1,9] [2,4] [4,7] [6,8]

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#3

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