The Smallest String Concatenation (Codeforces 632C)
Tags: Others, sortings

You're given a list of n strings a1, a2, ..., an. You'd like to concatenate them together in some order such that the resulting string would be lexicographically smallest.Given the list of strings, output the lexicographically smallest concatenation.

Input: The first line contains integer n — the number of strings (1 ≤ n ≤ 5·104).Each of the next n lines contains one string ai (1 ≤ |ai| ≤ 50) consisting of only lowercase English letters. The sum of string lengths will not exceed 5·104.

Output: Print the only string a — the lexicographically smallest string concatenation.


Sample Inputs:
4
abba
abacaba
bcd
er

5
x
xx
xxa
xxaa
xxaaa

3
c
cb
cba

Sample Outputs:
abacabaabbabcder

xxaaaxxaaxxaxxx

cbacbc

Solution (Python):
from sys import stdin
import functools

def cmp(a, b):
    if a + b > b + a:
        return 1
    else:
        return -1
n = int(input())
ls = []
for i in range(n):
    ls.append(stdin.readline().strip())
ls.sort(key=functools.cmp_to_key(cmp))
print(''.join(ls))

Solution (Python):
from functools import cmp_to_key
n = int(input())
a = []
for i in range(n):
    a.append(input())

def myCmp(x, y):
    if x + y < y + x:
        return -1
    else:
        return 1
a.sort(key=cmp_to_key(myCmp))
print(''.join(a))

Solution (Python):
from functools import cmp_to_key
n = int(input())
a = []
for i in range(n):
    a.append(input())

def myCmp(x, y):
    if x + y < y + x:
        return -1
    else:
        return 1
a.sort(key=cmp_to_key(myCmp))
print(''.join(a))