1.多次寻找并且不回溯

string s;
int pos = 0;
int n = s.size();
while(pos < n)
{
    pos = s.find("Alice",pos); //从pos位置开始寻找Alice
    if(pos == -1) break;

    pos++;
}
2.只找第一个位置

    int pos = s.find("Alice",0);
    if(pos == -1) cout << "没找到";