运行结果怎么是4247254和16384啊？我刚学c++不久

[qq1100119]

题目是：一个数，如果它是1到10，就把它设为0；如果是11到20，就设为-1；如果是21到30，就设为-2。
编译不出错啊，但是运行后显示就是4247254 16384 16384
麻烦各位老师帮帮我，怎么解决啊？
#include <iostream>
using namespace std;
int bo(int)
{
int x;
int s1[]={1,2,3,4,5,6,7,8,9,10};
int s2[]={11,12,13,14,15,16,17,18,19,20};
int s3[]={21,22,23,24,25,26,27,28,29,30};
for(int i=0;i!=10;i++)
{
if(x==s1[i])x=0;
if(x==s2[i])x=-1;
if(x==s3[i])x=-2;
}
return x;

}
int main(int argc, char *argv[])
{
cout<<bo(5)<<endl;
cout<<bo(11)<<endl;
cout<<bo(25)<<endl;
system("PAUSE");
return EXIT_SUCCESS;
}

[ri_aje]

int bo(int x)
{
  int s1[]={1,2,3,4,5,6,7,8,9,10};  
  int s2[]={11,12,13,14,15,16,17,18,19,20};  
  int s3[]={21,22,23,24,25,26,27,28,29,30};  
  for(int i=0;i!=10;i++)
  {
  if(x==s1[i])x=0;
  if(x==s2[i])x=-1;
  if(x==s3[i])x=-2;
  }
  return x;
    
}