1038 Recover the Smallest Number (30分)(贪心)

Given a collection of number segments, you are supposed to recover the smallest number from them. For example, given { 32, 321, 3214, 0229, 87 }, we can recover many numbers such like 32-321-3214-0229-87 or 0229-32-87-321-3214 with respect to different orders of combinations of these segments, and the smallest number is 0229-321-3214-32-87.

Input Specification:

Each input file contains one test case. Each case gives a positive integer N (≤) followed by N number segments. Each segment contains a non-negative integer of no more than 8 digits. All the numbers in a line are separated by a space.

Output Specification:

For each test case, print the smallest number in one line. Notice that the first digit must not be zero.

Sample Input:

5 32 321 3214 0229 87

Sample Output:

22932132143287

题目分析：贪心算法 没想明白 贪心算法利用局部最优而达到整个问题的最优解 
所以在compare中写的比较函数是 a+b与b+a进行比较

#define _CRT_SECURE_NO_WARNINGS
#include <climits>
#include<iostream>
#include<vector>
#include<queue>
#include<map>
#include<stack>
#include<algorithm>
#include<string>
#include<cmath>
using namespace std;
bool compare(const string& a, const string& b)
{
    return a + b < b + a;
}
int main()
{
    vector<string> S;
    int N;
    cin >> N;
    string s;
    for (int i = 0; i < N; i++)
    {
        cin >> s;
        S.push_back(s);
    }
    s = "";
    sort(S.begin(), S.end(), compare);
    for (auto it : S)
        s += it;
    while (s.length() && s.at(0) == '0')
        s.erase(s.begin());
    if (!s.length())cout << 0;
    else
        cout << s;
}