可能比一些题解稍微清楚些欢迎交流。

#include<iostream>
using namespace std;

int a[100005],b[100005];
int len=0,count=0;

bool check(int goal,int mid)
{
    if(goal<=mid) return 1;
    else return 0;
}

int find_half(int q[],int l,int r,int g)
{
    while(l<r)
    {
        int mid = l+r>>1;
        if(check(g,q[mid])) r=mid;
        else    l=mid+1;
    }

    if (q[l]==g)
    return l;

    else 
    return 10006;
}

int find_max(int q[],int g,int now)
{
    int you = now;
    while (q[++you]==g);  return you-1;
}

int find_min(int q[],int g,int now)
{
    int zuo = now;
    while (q[--zuo]==g) ; return zuo+1;
}



int main()
{
    cin>>len>>count;
    for(int i=0;i<len;i++)
    cin>>a[i];
    for(int i=0;i<count;i++)
    cin>>b[i];
    for(int i=0;i<count;i++)
    {
      if(find_half(a,0,len-1,b[i])==10006)  cout<<"-1"<<' '<<"-1"<<endl;
      else
      cout<<find_min(a,b[i],find_half(a,0,len-1,b[i]))<<' '<<find_max(a,b[i],find_half(a,0,len-1,b[i]))<<endl;


    }
}