#C++PrimerPlus# Chapter11_Exersice2_randwalk

本文介绍了一个基于C++的随机行走模拟程序。通过对randwalk.cpp的修改，该程序能够针对指定的目标距离和步长进行多次模拟实验，并统计每次实验所需的步数，最终输出这些步数的最大值、最小值及平均值。

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在Example13,Example14,Example15的例程中修改randwalk.cpp中的主函数，使的程序能对给定目标距离和步幅值重复多次计算，并统计随机的结果，给出最大值，最小值，平均值。

vector.h,vector.cpp可以不做修改，修改后的randwalk.cpp程序清单如下：

// randwork.cpp
#include <iostream>
#include <cstdlib>
#include <ctime>
#include "vector.h"
int main()
{
   using namespace std;
   using VECTOR::Vector;
   srand(time(0));
   double direction;
   Vector step;
   Vector result(0.0, 0.0);
   unsigned long steps = 0;
   double target;
   double dstep;
   int times;
   cout << "Enter target distance (q to quit): ";
   while (cin >> target)
   {
       cout << "Enter step length: ";
       if (!(cin >> dstep))
           break;
       cout << "Enter how mang times: ";
       if (!(cin >> times))
           break;

       unsigned long* steps = new unsigned long [times];

       for (int i = 0; i < times; i++)
       {
           steps[i] = 0;
           while (result.magval() < target)
           {
               direction = rand() % 360;
               step.reset(dstep, direction, Vector::POL);
               result = result + step;
               steps[i]++;
           }
           cout << "#" << i+1 << ": " << steps[i] << endl;
           result.reset(0.0, 0.0);
       }

       unsigned long sMax, sMin, sSum;
       sMax = steps[0];
       for (int i = 1; i < times; i++)
           sMax = sMax < steps[i] ? steps[i] : sMax;
       sMin = steps[0];
       for (int i = 1; i < times; i++)
           sMin = sMin > steps[i] ? steps[i] : sMin;
       sSum = steps[0];
       for (int i = 1; i < times; i++)
           sSum += steps[i];

       cout << "Max: " << sMax << ", Min: " << sMin << endl;
       cout << "Average: " << sSum / times << endl;

       for (int i = 0; i < times; i++)
           steps[0] = 0;
       cout << "Enter target distance (q to quit): ";
   }
   cout << "Bye!\n";
   cin.clear();
   while (cin.get() != '\n')
       continue;
   return 0;
}