1006 等差数列

#include <bits/stdc++.h>using namespace std;int n;int c = 2;int m = 0;int num [110];int main (){        cin >> n;        for (int i = 0; i < n; i ++){                cin >> num [i];        }        sort (num, num + n);        for (int i = 0; i < n - 1; i ++){                for (int j = i + 1; j < n; j ++){                        for (; ;){                                for (int k = j + 1; k < n; k ++){                                        if (num [k] == num [i] + c * (num [j] - num [i])){                                                c ++;                                        }                                        if (num [k] > num [i] + c * (num [j] - num [i])){                                                break;                                        }                                }                                break;                        }                        m = max (m, c);                        c = 2;                }        }        if (n == 1)                cout << '1';        else                cout << m;        return 0;}