cpp: pointer

 指针读二维数组

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int arr[3][4] = { {14,2,3,14},{14,5,6,7} ,{18,9,10,11} }; int* p; p = arr[0]; for (int i = 0; i < sizeof(arr) / sizeof(int); i++) {     cout <<"\t"<< &arr[i] << endl;     //p = arr[i];     cout << *p++ << endl; }

　　

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int* t; t = &arr[0][0]; for (int kk = 0; kk < 3; kk++) {       for (int Column = 0; Column < (sizeof(arr[kk]) / sizeof(arr[0][kk])); Column++)     {         cout << *t++ << endl;     } } int(*pp)[4]; //Column 4 int i, j; for (i = 0; i < 3; i++) {     pp = &arr[i];     cout << "Row" << i << ":";     for (j = 0; j < 4; j++)         cout << "\t" << *(*pp + j);     cout << endl; }   std::vector<int> v {3, -4, 2, -8, 15, 267};   auto print = [](const int& n) { std::cout << n << ' '; };   std::cout << "before:\t"; std::for_each(v.cbegin(), v.cend(), print); std::cout << '\n';   // increment elements in-place std::for_each(v.begin(), v.end(), [](int& n) { n++; });   std::cout << "after:\t"; std::for_each(v.cbegin(), v.cend(), print); std::cout << '\n';   struct Sum {     void operator()(int n) { sum += n; }     int sum{ 0 }; };   // invoke Sum::operator() for each element Sum s = std::for_each(v.cbegin(), v.cend(), Sum()); std::cout << "sum:\t" << s.sum << '\n';

　　

 

 

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/// <summary> /// 整数转二进制 /// </summary> /// <param name="n">整数</param> /// <param name="len">显示几位，如5位</param> /// <returns></returns> string  GeovinDu::DecimalToBinary(int n, int len) {     string ss = "";     int binaryNumber[100], num = n;     int i = 0;     while (n > 0) {         binaryNumber[i] = n % 2;         n = n / 2;         i++;     }     //cout << "Binary form of " << num << " is ";     std::string new_string = "";     for (int j = i - 1; j >= 0; j--)         ss = ss + to_string(binaryNumber[j]);     if (ss.length() < len)         new_string = std::string(len - ss.length(), '0') + ss;     else         new_string = ss;     return new_string; }

　　

 

 

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/// <summary>   /// 获取二进制字符串含“1”字符占位的序号集合（从零开始的连续序号）   /// </summary>   /// <param name="str">二进制字符串集合</param>   /// <param name="len">第几位</param>   /// <returns></returns>   vector<int> GeovinDu::getOneInt(vector <string> str,int len)   {         vector<int> nn;       int k = 0;       for (string ss : str)       {                      if (ss.substr(len, 1) == "1")           {               nn.push_back(k);           }           k++;       }       return nn;   }     /// <summary>   /// 读心术   /// </summary>   void GeovinDu::displayReadHeart()   {       int number = 0;       char input;       cout << "***" << endl;       int num[32];       for(int i=0;i<=31;i++)       {           num[i] = i;                  }       vector<string> strnum;       for (int i = 0; i <= 31; i++)       {           string ssd = bitset<5>(num[i]).to_string();           strnum.push_back(DecimalToBinary(num[i],5));                }       int i = 0;       for (string s : strnum)       {           cout <<i<<":"<< s << endl;           i++;       }       vector<int> nn;       nn = getOneInt(strnum, 0);       string str = "";       for (int d : nn)       {          // cout << d << endl;           str = ""+str + to_string(d)+"  ";       }         cout << "猜出心中所想数" << endl;       cout << str << endl;       cout << "请你选好之后，输入Y即可正式进入猜数游戏" << endl;       cin >> input;       if (input == 'Y' || input == 'y')       {           number = 16;       }       nn = getOneInt(strnum, 1);       str = "";       for (int d : nn)       {          // cout << d << endl;           str = "" + str + to_string(d) + " ";       }       cout << str << endl;       cout << "1请你回答是否有猜中数YES和NO，输入Y或N即可" << endl;       cin >> input;       if (input == 'Y' || input == 'y')       {           number += 8;       }       nn = getOneInt(strnum, 2);       str = "";       for (int d : nn)       {           // cout << d << endl;           str = "" + str + to_string(d) + " ";       }       cout << str << endl;       cout << "2请你回答是否有猜中数YES和NO，输入Y或N即可" << endl;       cin >> input;       if (input == 'Y' || input == 'y')       {           number += 4;       }       nn = getOneInt(strnum, 3);       str = "";       for (int d : nn)       {           // cout << d << endl;           str = "" + str + to_string(d) + " ";       }       cout << str << endl;       cout << "3请你回答是否有猜中数YES和NO，输入Y或N即可" << endl;       cin >> input;       if (input == 'Y' || input == 'y')       {           number += 2;       }       nn = getOneInt(strnum, 4);       str = "";       for (int d : nn)       {           // cout << d << endl;           str = "" + str + to_string(d) + " ";       }       cout << str << endl;       cout << "4请你回答是否有猜中数YES和NO，输入Y或N即可" << endl;       cin >> input;       if (input == 'Y' || input == 'y')       {           number += 1;       }         cout << "猜中你想的数：" << number << endl;     }