挑战程序设计竞赛POJ-2718Smallest Difference

题目
全排列。直接用next_permutation穷举所有情况。
坑点：0不能放在数字的开头比如012，这属于非法数字，只有作为0的时候才有意义。

#include <iostream>
#include <cstdio>
#include <cmath>
#include <iomanip>
#include <vector>
#include <stack>
#include <cstring>
#include <algorithm>
using namespace std;

int N;
int arr[11];

int main()
{
    cin >> N;
    while (N--) {
        int cnt = 0, num;
        char c;
        while (1) {
            scanf("%d%c", &num, &c);
            arr[cnt++] = num;
            if (c == '\n') {
                break;
            }
        }
        int l = cnt / 2 - 1, r = cnt / 2;
        int min_diff = 1e9 + 1;
        do {
            int L = 0, R = 0;   
            if ((l - 0 > 0 && arr[0] == 0) || (cnt - 1 - r > 0 && arr[r] == 0)) {
                continue;
            }
            for (int i = l, k = 1; i >= 0; i--, k *= 10) {
                L += arr[i] * k;
            }
            for (int i = cnt - 1, k = 1; i >= r; i--, k *= 10) {
                R += arr[i] * k;
            }
            min_diff = min(min_diff, abs(L - R));
        } while (next_permutation(arr, arr + cnt));
        cout << min_diff << endl;
    }
    return 0;
}