LeetCode - Largest Number

Largest Number

2015.1.23 20:24

Given a list of non negative integers, arrange them such that they form the largest number.

For example, given [3, 30, 34, 5, 9], the largest formed number is 9534330.

Note: The result may be very large, so you need to return a string instead of an integer.

Solution:

　　Sort the numbers and piece them together, you'll get the answer, either largest or smallest. As for how to sort them, please see the comparator().

　　Time complexity is O(n * log(n)), space complexity may be the same, or less.

Accepted code:

 1 //#define ZZ

 2 #include <algorithm>

 3 #include <cstdio>

 4 #include <iostream>

 5 #include <string>

 6 #include <vector>

 7 using namespace std;

 8 

 9 bool comparator(const string &s1, const string &s2)

10 {

11     string s12, s21;

12 

13     s12 = s1 + s2;

14     s21 = s2 + s1;

15 

16     bool res = s12 < s21;

17     s12.clear();

18     s21.clear();

19 

20     return res;

21 }

22 

23 class Solution {

24 public:

25     string largestNumber(vector<int> &num) {

26         char s[100];

27         vector<string>vs;

28 

29         int n, i;

30 

31         n = (int)num.size();

32         for (i = 0; i < n; ++i) {

33             sprintf(s, "%d", num[i]);

34             vs.push_back(string(s));

35         }

36 

37         sort(vs.begin(), vs.end(), comparator);

38         string res = "";

39 

40         for (i = n - 1; i >= 0; --i) {

41             res += vs[i];

42         }

43         vs.clear();

44 

45         i = 0;

46         n = (int)res.length();

47         while (i < n - 1 && res[i] == '0') {

48             ++i;

49         }

50         res = res.substr(i, n - i);

51 

52         return res;

53     }

54 };

55 

56 #ifdef ZZ

57 int main()

58 {

59     vector<int> num;

60     int n;

61     int i;

62     Solution sol;

63 

64     while (cin >> n) {

65         num.resize(n);

66         for (i = 0; i < n; ++i) {

67             cin >> num[i];

68         }

69         cout << sol.largestNumber(num) << endl;

70         num.clear();

71     }

72 

73     return 0;

74 }

75 #endif