poj 3096 Surprising Strings

#include <iostream>#include <cstdio>#include <cstdlib>#include <cstring>#include <cmath>using namespace std;#define maxn 100string st;char pairs[maxn][2];bool ok(char a, char b, int x){    for (int i = 0; i < x; i++)        if (pairs[i][0] == a && pairs[i][1] == b) return false;    pairs[x][0] = a;    pairs[x][1] = b;    return true;}int main(){       while (getline(cin, st) && st != "*")    {        int n = st.length();        bool s = true;        for (int i = 1; i < n - 1; i++)        { for (int j = 0; j + i < n; j++) {     if (!ok(st[j], st[i + j], j))     {         s = false;         break;     } } if (!s)     break;        }        if (s) cout << st << " is surprising.n";        else cout << st << " is NOT surprising.n";    }    return 0;}