提交记录 14378
提交时间 |
评测时间 |
2020-09-25 14:29:14 |
2020-09-25 14:30:20 |
#include "router.h"
#include <cstdint>
#include <vector>
#include <netinet/in.h>
std::vector<RoutingTableEntry> table;
/**
* @brief 插入/删除一条路由表表项
* @param insert 如果要插入则为 true ,要删除则为 false
* @param entry 要插入/删除的表项
*
* 插入时如果已经存在一条 addr 和 len 都相同的表项,则替换掉原有的。
* 删除时按照 addr 和 len **精确** 匹配。
*/
void update(bool insert, RoutingTableEntry entry) {
if (insert) {
for (auto &e:table) {
if (e.addr == entry.addr && e.len == entry.len) {
e.nexthop = entry.nexthop;
return;
}
}
table.push_back(entry);
} else {
for (auto it = table.begin(); it != table.end(); ++it) {
if (it->addr == entry.addr && it->len == entry.len) {
table.erase(it);
return;
}
}
}
}
/**
* @brief 进行一次路由表的查询,按照最长前缀匹配原则
* @param addr 需要查询的目标地址,网络字节序
* @param nexthop 如果查询到目标,把表项的 nexthop 写入
* @return 查到则返回 true ,没查到则返回 false
*/
bool prefix_query(uint32_t addr, uint32_t *nexthop) {
int max_len = -1;
uint32_t addr_q = ntohl(addr);
for (auto &e:table) {
uint32_t addr_e = ntohl(e.addr);
uint32_t addr_xor = addr_q ^addr_e;
uint32_t mask = 0x80000000;
int i;
for (i = 0; i < e.len; ++i) {
if (addr_xor & mask) {
i = -1;
break;
}
mask >>= 1;
}
if (i > max_len) {
max_len = i;
*nexthop = e.nexthop;
}
}
return max_len > -1;
}
void init(int n, int q, const RoutingTableEntry *a) {
for (int i = 0; i < n; ++i) {
update(true, a[i]);
}
}
unsigned query(unsigned addr) {
unsigned nexthop;
bool res = prefix_query(addr, &nexthop);
return res && nexthop;
}
Compilation | N/A | N/A | Compile OK | Score: N/A | 显示更多 |
Testcase #1 | 13.88 us | 24 KB | Accepted | Score: 25 | 显示更多 |
Testcase #2 | 30 s | 20 MB + 284 KB | Time Limit Exceeded | Score: 0 | 显示更多 |
Testcase #3 | 30 s | 20 MB + 284 KB | Time Limit Exceeded | Score: 0 | 显示更多 |
Testcase #4 | 30 s | 20 MB + 284 KB | Time Limit Exceeded | Score: 0 | 显示更多 |
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