179. Largest Number

Difficulty: Medium

Frequency: N/A

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.

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Code:
class Solution {
public:
string largestNumber(vector<int>& nums) {
sort(nums.begin(), nums.end(), compare);
string result;
for (int i = nums.size() - 1; i >= 0; i--) {
result += to_string(nums[i]);
}
if (result.find_first_not_of('0') == string::npos) return "0";
else return result = result.substr(result.find_first_not_of('0'));
}
private:
static bool compare(int& num1, int& num2) {
string s1 = to_string(num1);
string s2 = to_string(num2);
if ((s1 + s2) < (s2 + s2)) return true;
else return false;
}
};

Another solution:
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Things to learn: