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#include <iostream> #include <vector> using namespace std; int main(){ //test1 数组就是指针 /* string ar[] = {"aa","bb"}; string* p = ar; *p = "cc"; string* p1 = &ar[1]; *p1 = "dd"; for(auto s : ar){ cout << s; } cout << endl; */ //test2 用auto声明,得到的是指针 /* int ia[] = {1,2,3,5}; //ia1为整数指针 auto ia1(ia); *ia1 = 9; auto ia2(&ia[3]); *ia2 = 8; for(auto s : ia){ cout << s << ","; } cout << endl; */ //test3 用decltype声明,得到的不是指针 /* int ia[3]; decltype(ia) ia3 = {2,3,4}; //ia3 = &ia[0];//编译错误 ia3[2] = 9; for(auto s : ia3){ cout << s << ","; } cout << endl; */ //test4 用指针模拟end /* int arr[] = {0,1,2}; int* end = &arr[3]; for(int* beg = arr;beg != end; ++ beg){ cout << *beg; } cout << endl; */ //test5 标准库函数std::begin,std::end /* int arr[] = {0,1,2}; int* beg = std::begin(arr); //int* end = &arr[3]; int* end = std::end(arr); for(;beg != end; ++ beg){ cout << *beg; } cout << endl; */ //test6 ptrdiff_t和size_t //ptrdiff是数组下标相加减的值的类型,size_t是数组下标的类型 /* int arr[] = {1,2,3,4,5}; int* b = std::begin(arr); int* e = std::end(arr); ptrdiff_t juli = e - b - 1; cout << juli << endl; size_t sz = juli; cout << arr[sz] << endl; */ //test7 数组的下标可以是负值,标准库的string,vector的下标也可以是负值 /* int ia[] = {1,2,3,4,5}; int* p = &ia[2]; int j = p[1];//相当于*(p + 1),也就是ia[3] cout << j << endl; int k = p[-2];//相当于*(p - 2),也就是ia[0] cout << k << endl; string s("abcde"); char* p1 = &s[2]; cout << p1[-1] << endl; vector<int> v{1,2,3,4}; int* p2 = &v[3]; cout << p2[-2] << endl; */ //test8 用数组初始化vector,注意生成的vector里的元素不包括第二个参数 /* int ia[] = {0,1,2,3,4,5,6}; vector<int> v(std::begin(ia), std::end(ia)); for(auto s : v){ cout << s << ","; } cout << endl; vector<int> v1(ia + 1, ia + 4); for(auto s : v1){ cout << s << ","; } cout << endl; */ }
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