longest prefix matching 是什么意思

longest prefix matching 是一种网络路由技术，用于在路由表中查找与目标 IP 地址最匹配的前缀。在路由表中，每个条目都包含一个 IP 前缀和一个下一跳地址。当路由器收到一个数据包时，它会从数据包的目标 IP 地址中提取前缀，并在路由表中查找与该前缀最匹配的条目。最匹配的条目指的是，它的前缀与目标 IP 地址的前缀最长且匹配，这被称为 longest prefix matching。通过这种方式，路由器可以确定数据包的下一跳地址，并将其转发到正确的位置。这种技术广泛应用于互联网路由和数据中心网络中。

相关问题

Consider a datagram network using 32-bit host addresses. Suppose a router has four links, numbered 0 through 3, and packets are to be forwarded to the link interfaces as follows: Destination Address Range Link Interface 11100000 00000000 00000000 00000000 through 11100000 00111111 11111111 11111111 0 11100000 01000000 00000000 00000000 through 11100000 01000000 11111111 11111111 1 11100000 01000001 00000000 00000000 through 11100001 01111111 11111111 11111111 2 Otherwise 3 1) Provide a forwarding table that has five entries, uses longest prefix matching, and forwards packets to the correct link interfaces. (6 points) Prefix Match Link Interface

Prefix Match Link Interface
11100000 00000000 00000000 00000000 through 11100000 00111111 11111111 11111111 0
11100000 01000000 00000000 00000000 through 11100000 01000000 11111111 11111111 1
11100000 01000001 00000000 00000000 through 11100001 01111111 11111111 11111111 2
Default (otherwise) 3

longestCommonPrefix(vector<string>& strs)什么意思

words) function?

The longestCommonPrefix function takes a vector of strings as input and returns a string that is the longest common prefix among all the strings in the vector. The function works by comparing the characters of the strings in the vector starting from the first character and returning the prefix that is common among all the strings.

Here is the code for the longestCommonPrefix function:

string longestCommonPrefix(vector<string>& words) {
    if (words.empty()) return "";
    string prefix = words[0];
    for (int i = 1; i < words.size(); i++) {
        int j = 0;
        while (j < prefix.size() && j < words[i].size() && prefix[j] == words[i][j]) {
            j++;
        }
        prefix = prefix.substr(0, j);
        if (prefix.empty()) return "";
    }
    return prefix;
}

The function first checks if the vector is empty and returns an empty string if it is. It then initializes the prefix string to the first string in the vector. The function then loops through the rest of the strings in the vector, comparing each character of the prefix string with the corresponding character of the current string in the loop. If the characters match, the loop continues to the next character. If the characters do not match, the function updates the prefix string to only include the characters up to and including the last matching character. If the prefix string becomes empty, the function returns an empty string. Once the loop has finished, the function returns the final prefix string that is common among all the strings in the vector.