Exercise using STL sort to sort containers

The main exercise is to use std: sort to sort std: vector, std: string, etc, you can also learn how to customize a sorting rule by specifying a custom sorting method or reloading the operator. [Cpp] # include <string> # include <vector> # include <algorithm> # include <functional> # include <iostream> struct Vec2D {float x; float y; Vec2D (): x (0.f), y (0.f) {} Vec2D (float fx, float fy): x (fx), y (fy) {}}; std :: ostream & operator <(std: ostream & out, const Vec2D & val) {return out <"<val. x <"," <val. y <")" ;}struct Vec3D {float x; float y; float z; Vec3D (): x (0.f), y (0.f), z (0.f ){} Vec3D (float fx, float fy, float fz): x (fx), y (fy), z (fz) {} float length_squared () const {return x * x + y * y + z * z;} float length () const {return sqrtf (length_squared ();} bool operator <(const Vec3D & rhs) {return length_squared () <rhs. length_squared () ;}}; std: ostream & operator <(std: ostream & out, const Vec3D & val) {return out <"(" <val. x <"," <val. y <"," <val. z <")";} templa Te <class T> void print_vector (const std: vector <T> & v) {using std: cout; using std: endl; for (std :: vector <T>: const_iterator iter = v. begin (); iter! = V. end (); ++ iter) {cout <(* iter) <"\ t" ;}cout <endl ;}// vector <int> sorting method, here, the static bool sort_comp_int (int elem1, int elem2) {return abs (elem1) <abs (elem2);} // vector <Vec2D> sorting method is sorted in ascending order of absolute values, here, sort by x from large to small. If x is the same, then sort by y from small to large static bool sort_comp_Vec2D (const Vec2D & elem1, const Vec2D & elem2) {if (elem1.x> elem2.x) return true; else if (elem1.x = elem2.x) return elem1.y <elem2.y; return false;} in T main (int argc, char ** argv) {using std: cout; using std: cin; using std: endl; cout <"========= sort std :: vector <int >================= "<endl; std: vector <int> vi; vi. push_back (3); vi. push_back (-4); vi. push_back (1); vi. push_back (5); cout <"before sort:" <endl <"\ t"; print_vector <int> (vi ); // use the default Sorting Algorithm (operator <) from small to large sorting std: sort (vi. begin (), vi. end (); cout <"sort default:" <endl <"\ t"; print _ Vector <int> (vi); // use the descending order algorithm std: sort (vi. begin (), vi. end (), std: greater <int> (); cout <"sort greater:" <endl <"\ t "; print_vector <int> (vi); // use the custom Sorting Algorithm std: sort (vi. begin (), vi. end (), sort_comp_int); cout <"sort user defined:" <endl <"\ t"; print_vector <int> (vi ); //////////////////////////////////////// /// // cout <"= ========= sort std:: string ============== ==== "<Endl; std: string s =" Hello, world! "; Cout <" before sort: "<endl <" \ t "; cout <s <endl; std: sort (s. begin (), s. end (); cout <"sort default:" <endl <"\ t"; cout <s <endl; //////////////////////////////////////// /// // cout <"= ========= sort std:: vector <Vec2D >=============== "<endl; std: vector <Vec2D> v2; v2.push _ back (Vec2D (3.f,-1.f)); v2.push _ back (Vec2D (1.f, 6.f)); v2.push _ back (Vec2D (3.f, 3.2f); v2.push _ Back (Vec2D (2.f, 0.f)); cout <"before sort:" <endl <"\ t"; print_vector <Vec2D> (v2 ); // use the custom Sorting Algorithm std: sort (v2.begin (), v2.end (), sort_comp_Vec2D); cout <"sort user defined: "<endl <" \ t "; print_vector <Vec2D> (v2 ); //////////////////////////////////////// /// // cout <"= ========= sort std:: vector <Vec3D >=============== "<endl; std: vector <Vec3D> v3; v3.push _ back (Vec3D (1.f, 0. f, 0.f)); v3.push _ back (Vec3D (1.f, 1.f, 1.f)); v3.push _ back (Vec3D (0.f, 2.f, 0.f)); v3.push _ back (Vec3D (0.f, 1.f, 1.f )); cout <"before sort:" <endl <"\ t"; print_vector <Vec3D> (v3); // The default sorting algorithm uses operator <as the sorting method std:: sort (v3.begin (), v3.end (); cout <"sort operator <:" <endl <"\ t"; print_vector <Vec3D> (v3 ); cin. get (); return EXIT_SUCCESS;} output result: [plain] ========== sort std :: vector <int >=========== ==== Before sort: 3-4 1 5 sort default:-4 1 3 5 sort greater: 5 3 1-4 sort user defined: 1 3-4 5 ========== sort std: string ==================== before sort: Hello, world! Sort default :!, Hdellloorw ========= sort std: vector <Vec2D >====================== before sort: (3, -1) (3.2) (3, 3.2) () sort user defined: www.2cto.com (3,-1) (3) ========= sort std: vector <Vec3D >====================== before sort, 0) (, 1) (, 0) (, 1) sort operator <: (, 0) (, 1) (, 1) (, 1, 0)