......
随机测试代码：

#include<bits/stdc++.h>
using namespace std;
int main()
{
    int sj,i=0;
    long long sum=0;
    string s;
    cout<<"随机查找：";
    cin>>s;
    srand(time(0));
    while(true)
    {
        sj=rand()%96;
        cout<<char('!'+sj);
        if(s[i++]!=char('!'+sj))
        {
            i=0,sum++;
            cout<<" ";
        }
        if(i==s.size())break;
    }
    cout<<"\n\n共执行"<<sum<<"次\n概率"<<1.0/sum*100.0<<"%"; 
    return 0;
}