Introduction to Sorting

C++

Java

Python

C++

In order to sort a dynamic array, use sort(v.begin(), v.end()) (or sort(begin(v),end(v))), whereas static arrays require sort(arr, arr + N) where $N$ is the number of elements to be sorted. The default sort function sorts the array in ascending order.

Java

In order to sort a static or dynamic array, use Arrays.sort(arr) or Collections.sort(list) respectively. The default sort function sorts the array in ascending order.

• Arrays.sort
• Collections.sort

See here for an example of a solution that was hacked on CodeForces.

Two ways to avoid this:

• Declare the underlying array as an array of objects, for example Long instead of long. This forces the Arrays.sort() function to use mergesort, which is always $\mathcal{O}(N\log N)$.
• Shuffle the array beforehand.

Python

In order to sort a list, simply use the sorted(list) function.

• Sorting Basics

C++

By default, C++ pairs are sorted by first element and then second element in case of a tie.

1// Source: CPH
2
3#include <bits/stdc++.h>
4using namespace std;
5
6int main() {
7    vector<pair<int,int>> v;
8    v.push_back({1,5});
9    v.push_back({2,3});
10    v.push_back({1,2});

Tuples are sorted similarly.

Java

You'll need to define your own custom comparator. This is covered in Silver.

Python

By default, Python tuples sort by first element, then second element, and so on in case of repeated ties.

1list = [(1, 2), (2, 3), (2, 1), (3, 1)]
2list = sorted(list)
3for x, y in list:
4    print(f'{x}, {y}')
5
6# Output:
7# 1, 2
8# 2, 1
9# 2, 3
10# 3, 1