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