Question

我希望在列表中看到一个数字大于它后面的数字的次数。

example = [2, 3, 4, 5, 7, 8, 6, 2, 3, 4, 5]

def lstCount(lst):
    counter = 0
    if lst[0] < lst[1]:
        counter + 1 
        lstCount(lst[1:])
    else:
        lstCount(lst[1:])

    return counter

lstCount(example)

这应该产生2，但我得到列表索引超出范围。

Answer 1

#include "stdafx.h"
#include "cli.h"

cli::cli(char *ip)
{
    //WSA
    {
        WORD wVersionRequested;
        WSADATA wsaData;
        int err;

        // Use the MAKEWORD(lowbyte,highbyte) macro declared in windef.h
        wVersionRequested = MAKEWORD(2, 2);

        err = WSAStartup(wVersionRequested, &wsaData);

        if (err != 0)
        {
            std::cout << "WSAStartup failed with the error: " << err;
        }
    }

    //get addressSize 
    addressSize = sizeof(address);

    //set address struct data members
    address.sin_family = AF_INET;
    address.sin_port = htons(444);

    //if ip empty, prompt user;
    if (ip == NULL)
    {
        std::string ipInput;
        std::cout << "\n\tConnect to which IP: ";
        std::cin >> ipInput;
        address.sin_addr.s_addr = inet_addr(ipInput.c_str());
    }
    else
    {
        address.sin_addr.s_addr = inet_addr(ip);
    }

    sock = socket(AF_INET, SOCK_STREAM, 0);

    std::cout << "\n\tYour username: ";
    std::cin >> uname;
}

cli::~cli()
{
}

void cli::start()
{
    try
    {
        //hold string
        char message[33];

        std::cout << "\n\tcli::start() called";
        int conRet;

        //connects to server socket & receives a message, stores in it message variable
        conRet = connect(sock, (sockaddr*)&address, (int)addressSize);
        recv(sock, message, sizeof(message), 0);

        std::cout << "\n\tSERVER: " << message;

        //starts threads, pass this for object scope.
        std::thread sendThread(&cli::cSend, this);
        std::thread recvThread(&cli::cRecv, this);

        //this function (start) will return/end when send and recv threads end.
        sendThread.join();
        recvThread.join();
    }
    catch (std::exception e)
    {
        std::cerr << e.what() << std::endl;
    }
}

void cli::cSend()
{
    std::cout << "\n\tcli::send thread started";
    //char arr for sending str;
    std::string getLine;
    while (true)
    {
        std::cout << "\n\t" << uname << ":" << std::flush;
        //set to "" because i suspected the value remains in the string after a loop.
        std::string message = "";

        //get input, put it in message
        std::getline(std::cin, message);

        //get full message
        std::string fullMessage = uname + ":" + message;

        //get constant int, size of fullMessage
        const int charArrSize = fullMessage.length();

        std::cout << "\t\tINFO: Sending character array of length: " << charArrSize << " size: " << sizeof(fullMessage.c_str()) << " : " << fullMessage.c_str() << std::endl;

        //sends it
        send(sock, fullMessage.c_str(), charArrSize, 0);
    }
}

void cli::cRecv()
{
    std::cout << "\n\tcli::recv  thread started";

    //initialize arr to 0, will hopefully help avoid the weird chars in the cout
    char recvMessage[256]{ '\0' };

    while (true)
    {
        recv(sock, recvMessage, sizeof(recvMessage), 0);

        std::cout << "\t\tINFO:Received message of length: " << std::strlen(recvMessage) << " size: " << sizeof(recvMessage) << " : " << recvMessage << std::endl;

        std::cout << recvMessage << std::endl;
    }
}

或者只是

it = iterator(lst)
next(it, None)
count = sum(a > b for a, b in zip(lst, it))

Answer 2

您需要添加一个基本情况，其中lst只有1个元素。否则，当它检查lst[1]时，它将尝试检查不存在的元素，并且您可以获得越界错误。另外counter + 1什么都不做。我建议只返回值而不是使用计数器。

def lstCount(lst):
    if len(lst) == 1:
        return 0
    elif lst[0] > lst[1]:
        return 1 + lstCount(lst[1:])
    return lstCount(lst[1:])

Answer 3

另一个直接解决方案：遍历第一个n-1个元素并比较列表中的当前和下一个元素。

example = [2, 3, 4, 5, 7, 8, 6, 2, 3, 4, 5]
count = 0
for i in range(len(example) - 1):#get size of example then decrease by 1
    if example[i] < example[i + 1]:#visit element by index
        count = count + 1
print count

Output:
8

如何计算列表中的数字大于之后的数字？

3 个答案: