我最近写了一个简短的算法来计算python中的快乐数字。该程序允许您选择一个上限，它将确定其下的所有快乐数字。为了进行速度比较，我决定对我知道的从python到c
++的算法进行最直接的翻译。

令人惊讶的是，c
版本的运行速度明显慢于python版本。执行时间之间的准确速度测试（用于发现前10,000个快乐数字）表明python程序平均在0.59秒内运行，而c
版本平均在8.5秒内运行。

我将这种速度差异归因于这样一个事实，即我必须为已经内置在python语言中的c
++版本的部分计算（例如，确定某个元素是否在列表/数组/向量中）编写辅助函数。 。

首先，这是造成如此荒谬的速度差异的真正原因，其次，我该如何更改c ++版本以比python版本更快地执行（我认为应该如此）。

经过速度测试的两段代码在这里：Python版本，C
++版本。谢谢您的帮助。

#include <iostream>
#include <vector>
#include <string>
#include <ctime>
#include <windows.h>

using namespace std;

bool inVector(int inQuestion, vector<int> known);
int sum(vector<int> given);
int pow(int given, int power);
void calcMain(int upperBound);

int main()
{
    while(true)
    {
        int upperBound;
        cout << "Pick an upper bound: ";
        cin >> upperBound;
        long start, end;
        start = GetTickCount();
        calcMain(upperBound);
        end = GetTickCount();
        double seconds = (double)(end-start) / 1000.0;
        cout << seconds << " seconds." << endl << endl;
    }
    return 0;
}

void calcMain(int upperBound)
{
    vector<int> known;
    for(int i = 0; i <= upperBound; i++)
    {
        bool next = false;
        int current = i;
        vector<int> history;
        while(!next)
        {
            char* buffer = new char[10];
            itoa(current, buffer, 10);
            string digits = buffer;
            delete buffer;
            vector<int> squares;
            for(int j = 0; j < digits.size(); j++)
            {
                char charDigit = digits[j];
                int digit = atoi(&charDigit);
                int square = pow(digit, 2);
                squares.push_back(square);
            }
            int squaresum = sum(squares);
            current = squaresum;
            if(inVector(current, history))
            {
                next = true;
                if(current == 1)
                {
                    known.push_back(i);
                    //cout << i << "\t";
                }
            }
            history.push_back(current);
        }
    }
    //cout << "\n\n";
}

bool inVector(int inQuestion, vector<int> known)
{
    for(vector<int>::iterator it = known.begin(); it != known.end(); it++)
        if(*it == inQuestion)
            return true;
    return false;
}

int sum(vector<int> given)
{
    int sum = 0;
    for(vector<int>::iterator it = given.begin(); it != given.end(); it++)
        sum += *it;
    return sum;
}

int pow(int given, int power)
{
    int original = given;
    int current = given;
    for(int i = 0; i < power-1; i++)
        current *= original;
    return current;
}

#!/usr/bin/env python

import timeit

upperBound = 0

def calcMain():
    known = []
    for i in range(0,upperBound+1):
        next = False
        current = i
        history = []
        while not next:
            digits = str(current)
            squares = [pow(int(digit), 2) for digit in digits]
            squaresum = sum(squares)
            current = squaresum
            if current in history:
                next = True
                if current == 1:
                    known.append(i)
                    ##print i, "\t",
            history.append(current)
    ##print "\nend"

while True:    
    upperBound = input("Pick an upper bound: ")
    result = timeit.Timer(calcMain).timeit(1)
    print result, "seconds.\n"