赛事写的屎山（71pts），这个随机化思路有没有进一步优化的空间？

#include <bits/stdc++.h>
#define lb(x) (x&-x)
#define L(i,j,k) for(int i=(j);i<=(k);++i)
#define R(i,j,k) for(int i=(j);i>=(k);--i)
#define swap(a,b) (a^=b^=a^=b)

using namespace std;
using i64 = long long;

const int maxn = 3e5 + 10, mod = 998244353;
typedef pair<int,int> pii;
typedef long long ll;
typedef unsigned long long ull;
void chmin(int &x,int c){x=min(x,c);}
void chmax(int &x,int c){x=max(x,c);}

namespace fast_IO {
#define IOSIZE 100000
int precision=3,POW[10]={1,10,100,1000,10000,100000,1000000,10000000,100000000,1000000000};char ibuf[IOSIZE],obuf[IOSIZE],*p1=ibuf,*p2=ibuf,*p3=obuf;
#ifdef ONLINE_JUDGE
#define getchar() ((p1==p2)and(p2=(p1=ibuf)+fread(ibuf,1,IOSIZE,stdin),p1==p2)?(EOF):(*p1++))
#define putchar(x) ((p3==obuf+IOSIZE)&&(fwrite(obuf,p3-obuf,1,stdout),p3=obuf),*p3++=x)
#define isdigit(ch) (ch>47&&ch<58)
#define isspace(ch) (ch<33)
#endif
template<typename T>inline T read(){T s=0;int w=1;char ch;while(ch=getchar(),!isdigit(ch)&&(ch!=EOF))if(ch==45)w=-1;if(ch==EOF)return 0;while(isdigit(ch))s=s*10+ch-48,ch=getchar();return s*w;}template<typename T>inline bool read(T&s){s=0;int w=1;char ch;while(ch=getchar(),!isdigit(ch)&&(ch!=EOF))if(ch==45)w=-1;if(ch==EOF)return 0;while(isdigit(ch))s=s*10+ch-48,ch=getchar();return s*=w,1;}inline bool read(char&s){while(s=getchar(),isspace(s));return 1;}inline bool read(char*s){char ch;while(ch=getchar(),isspace(ch));if(ch==EOF)return 0;while(!isspace(ch))*s++=ch,ch=getchar();*s='\000';return 1;}template<typename T>inline void print(T x){if(x<0)putchar(45),x=-x;if(x>9)print(x/10);putchar(x%10+48);}inline void print(char x){putchar(x);}inline void print(char*x){while(*x)putchar(*x++);}inline void print(const char*x){for(int i=0;x[i];i++)putchar(x[i]);}inline bool read(std::string&s){s="";char ch;while(ch=getchar(),isspace(ch));if(ch==EOF)return 0;while(!isspace(ch))s+=ch,ch=getchar();return 1;}inline void print(std::string x){for(int i=0,n=x.size();i<n;i++)putchar(x[i]);}inline bool read(bool&b){char ch;while(ch=getchar(),isspace(ch));b=ch^48;return 1;}inline void print(bool b){putchar(b+48);}inline bool read(double&x){int a=0,b=0;char ch=getchar();bool f=0;while(ch<48||ch>57){if(ch==45)f=1;ch=getchar();}while(47<ch&&ch<58){a=(a<<1)+(a<<3)+(ch^48);ch=getchar();}if(ch!=46){x=f?-a:a;return 1;}ch=getchar();while(47<ch&&ch<58){b=(b<<1)+(b<<3)+(ch^48),ch=getchar();}x=b;while(x>1)x/=10;x=f?-a-x:a+x;return 1;}inline void print(double x){if(x<0){putchar(45),x=-x;}x=round((long double)x*POW[precision])/POW[precision],print((long long)x),putchar(46),x-=(long long)(x);for(int i=1;i<=precision;i++)x*=10,putchar(x+48),x-=(int)x;}template<typename T,typename...T1>inline int read(T& a,T1&...other){return read(a)+read(other...);}template<typename T,typename...T1>inline void print(T a,T1...other){print(a),print(other...);}struct Fast_IO{~Fast_IO(){fwrite(obuf,p3-obuf,1,stdout);}}io;template<typename T>Fast_IO& operator>>(Fast_IO&io,T&b){return read(b),io;}template<typename T>Fast_IO& operator<<(Fast_IO&io,T b){return print(b),io;}
#define cout io
#define cin io
#define endl '\n'
}using namespace fast_IO;
struct qwq{
    int a,b,id;
}q[maxn];
int n,m,mp[maxn],st[maxn],ed[maxn],res[maxn];
map<pair<int,int>,int>mp2;
void solve(){
    srand(time(0));
    cin>>n>>m;
    register int i;
    for(i=1;i<=m;i++){
        cin>>q[i].a>>q[i].b,q[i].id=i;
    }
    int cnt=0;
    for(i=1;i<=m;i++){
        mp[q[i].a]++;
        mp[q[i].b]++;
        mp2[{q[i].a,q[i].b}]++;
    }
    sort(q+1,q+1+m,[](qwq s1,qwq s2){
        return s1.a==s2.a?s1.b<s2.b:s1.a<s2.a;
    });
    // cout<<"---------------------\n";
    // for(int i=1;i<=m;i++){
    //     cout<<q[i].a<<' '<<q[i].b<<'\n';
    // }
    for(int i=1;i<=m;i++){
        int l=1,r=m;
        while(l<r){
            int mid=(l+r+1)>>1;
            if(q[mid].a>q[i].a)r=mid-1;
            else l=mid;
        }
        ed[i]=r;;
        l=1,r=m;
        while(l<r){
            int mid=(l+r)>>1;
            if(q[mid].a<q[i].a)l=mid+1;
            else r=mid;
        }
        st[i]=l;
    }
    // cout<<"--------------------\n";
    // for(int i=1;i<=m;i++){
    //     cout<<st[i]<<' '<<ed[i]<<'\n';
    // }
    // // cout<<cnt<<'\n';
    for(i=1;i<=m;i++){
        if(mp[q[i].a]+mp[q[i].b]-mp2[{q[i].a,q[i].b}]==m){
            continue;
        }
        int k=ed[i]-st[i]+1;
        while(1){
            int j=rand()%(m-k)+1;
            if(j>=st[i])j+=k;
            if(j==i)continue;
            // cout<<i<<' '<<j<<' '<<k<<' '<<q[i].a<<' '<<q[i].b<<' '<<q[j].a<<' '<<q[j].b<<'\n';
            int s=(q[j].a!=q[i].a)+(q[i].a!=q[j].b)+(q[i].b!=q[j].a)+(q[i].b!=q[j].b);
            if(s==4){
                res[q[i].id]=q[j].id;
                break;
            }
        }
    }
    for(i=1;i<=m;i++)cout<<res[i]<<" \n"[i==m];
}

signed main() {
  int T=1;
  while(T--)solve();
  return 0;
}