代码

//#define Debug 
#ifndef Debug
#include "router.h"
#include <netinet/in.h> 
#endif
#ifdef Debug
typedef struct {
    unsigned addr;
    unsigned char len;
    char pad[3];  // Padding for memory alignment
    unsigned nexthop;
} __attribute__((packed)) RoutingTableEntry;
#endif

#include <iostream>
#include <cstdlib>
unsigned ones_prefix[33];
unsigned mask_addr[33];
unsigned int ans=-1;
int maxlen=-1;
int n;
int q;
RoutingTableEntry *a;

void init(int _n, int _q, const RoutingTableEntry *_a) {
	n=_n;
	q=_q;
	a=(RoutingTableEntry*)_a;
	for (int i=1;i<=32;i++){
		ones_prefix[i]=ones_prefix[i-1]|(1<<(32-i));
	}
	for (int i=0;i<n;i++){
		a[i].addr=htonl(a[i].addr);
		a[i].addr&=ones_prefix[a[i].len];
	}
}


unsigned query(unsigned addr) {
	addr=htonl(addr);
	for (int i=1;i<=32;i++){
		mask_addr[i]=addr&ones_prefix[i];
	}

	for (int i=0;i<n;i++){
		if ((mask_addr[a[i].len]==a[i].addr)&&(a[i].len>maxlen)){
			maxlen=a[i].len;
			ans=a[i].nexthop;
		}
	}	
	if (maxlen==-1) return 0;
	return ans;
}

评测结果