sort and binary search in C++

int arr[] = {1, 5, 8, 9, 6, 7, 3, 4, 2, 0};

    int n = sizeof(arr)/sizeof(arr[0]);

 

    sort(arr, arr+n); //

0 1 2 3 4 5 6 7 8 9

sort in descending order?

sort(arr, arr+n, greater<int>()); //

9 8 7 6 5 4 3 2 1 0

sort in particular order?

// A C++ program to demonstrate STL sort() using

// our own comparator

#include

using namespace std;

 

// An interval has 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

       cout << "[" << arr[i].start << "," << arr[i].end

            << "] ";

 

    return 0;

}

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

------------

This searching only works when container is sorted.

 vector<int> arr = {10, 15, 20, 25, 30, 35};

     

    // using binary_search to check if 15 exists

    if (binary_search(arr.begin(), arr.end(), 15))

       cout << "15 exists in vector";

    else

       cout << "15 does not exist";