关键函数：string s s.substr(2,3)

s.find("ab",2)，如果没找到，返回-1

#include<iostream>
#include<string>
using namespace std;
int main(){
	string s;
	int dx = 0, xx = 0, sz = 0, qt = 0, zl = 0, cont = 0, find, time = 0;
	while (cin >> s){
		if (s.size() > 8){   //首先判断字符串长度
			for (int i = 0; i < s.size(); i++){
				if (s[i] >= '0'&&s[i] <= '9'){
					sz = 1;
				}
				if (s[i] >= 'A'&&s[i] <= 'Z'){
					dx = 1;
				}
				if (s[i] >= 'a'&&s[i] <= 'z'){
					xx = 1;
				}
				if (s[i]<'0' || (s[i]>'9'&&s[i]<'A') || (s[i]>'Z'&&s[i]<'a') || (s[i]>'z')){
					qt = 1;
				}
			}
			zl = sz + dx + xx + qt;
			if (zl >= 3){
				for (int k = 0; k < s.size() - 3; k++){
					string zc = s.substr(k, 3);
					find = s.find(zc, k + 3);
					if (find != -1){
						cont++;
					}
				}
				if (cont == 0){
					cout << "OK" << endl;
				}
				else{
					cout << "NG" << endl;
					cont = 0;
				}
			}

		}
		if (s.size() <= 8){
			cout << "NG" << endl;

		}
		if (zl < 3){
			cout << "NG" << endl;
		}
	}

	return 0;
}