主要練習使用 std::sort 對 std::vector, std::string 等進行排序，並學習如何通過指定自定義排序方法或者重載 operator < 操作符等方式來自定義排序規則。 [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<<")"; } template <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>排序方法，這裡按絕對值由小到大排序 static bool sort_comp_int(int elem1, int elem2) { return abs(elem1) < abs(elem2); } // vector<Vec2D>排序方法，這裡先按x由大到小排序，如果x相同再按y由小到大排序 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; } int 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); // 使用默認的排序算法(operator <)由小到大排序 std::sort(vi.begin(), vi.end()); cout<<"sort default: "<<endl<<"\t"; print_vector<int>(vi); // 使用 STL 提供的由大到小的排序算法 std::sort(vi.begin(), vi.end(), std::greater<int>()); cout<<"sort greater: "<<endl<<"\t"; print_vector<int>(vi); // 使用自定義的排序算法 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); // 使用自定義排序算法 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); // 默認的排序算法使用 operator < 作為排序方法 std::sort(v3.begin(), v3.end()); cout<<"sort operator <: "<<endl<<"\t"; print_vector<Vec3D>(v3); cin.get(); return EXIT_SUCCESS; } 輸出結果： [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) (1,6) (3,3.2) (2,0) sort user defined: www.2cto.com (3,-1) (3,3.2) (2,0) (1,6) ========== sort std::vector<Vec3D> =============== before sort: (1,0,0) (1,1,1) (0,2,0) (0,1,1) sort operator <: (1,0,0) (0,1,1) (1,1,1) (0,2,0)
