CSS 342 Data Structures, Algorithms, and Discrete Mathematics I. Standard Template Library

Transcription

1 CSS 342 Data Structures, Algorithms, and Discrete Mathematics I Standard Template Library 1

2 Standard Template Library Need to understand basic data types, so we build them ourselves Once understood, we can more easily use Standard Template Library 2

3 Standard Template Library Sequence Containers: array - fixed size, direct access to any element vector - fast insert, fast delete at back, direct access to any element. deque - fast insertions and deletions at front or back, double ended queue list - doubly linked list, fast insertion and deletion anywhere Associative Containers: set - fast lookup, no duplicates map - one to one mapping, no duplicates allowed, fast key-based lookup Container Adapters: stack - last-in, first-out queue - first-in, last-out priority_queue - highest-priority element is always first out 3

4 #include <vector> vector<int> v{5, 10, 20, 40, 80; // can use auto const& instead of const int& for (const int& item: v) cout << item << " "; cout << endl; // access an element directly cout << "Element at 2: " << v.at(2) << endl; cout << "Element at 2: " << v[2] << endl; // access an element directly cout << "Element at front: " << v.front() << endl; cout << "Element at back: " << v.back() << endl; // vector<int>::iterator vx = v.begin(); auto vi = v.begin(); cout << "*vi is : " << *vi << endl; // 5 vi = vi + 2; cout << "*vi is : " << *vi << endl; // 20 4

5 #include <algorithm> // keep them sorted sort(v.begin(), v.end(), [](int &a, int &b) { return a < b; ); bool intcompare(const int &a, const int &b) { return a < b; sort(v.begin(), v.end(), intcompare); // function object class IntCompareClass { public: bool operator()(const int &a, const int &b) { return a < b; ; sort(v.begin(), v.end(), IntCompareClass()); 5

6 // inserting 15 as element index 2 v.insert(vi, 15); cout << "Element at 2 after insert: " << v.at(2) << endl; vi = v.end(); // *v1 is undefined // cout << "*vi is : " << *vi << endl; vi--; cout << "*vi is : " << *vi << endl; // 80 for (auto iter = v.begin(); iter!= v.end(); ++iter) cout << *iter << " "; cout << endl; 6

7 #include <set> void testset() { set<string> s; s.insert("rose"); s.insert("lily"); if (s.count("rose")) { cout << "Rose is in the set" << endl; else { cout << "Rose is not in the set" << endl; for (const auto& item: s) cout << item << ", "; cout << endl; 7

8 #include <map> void testmap() { map<int, string> ms; ms[25] = "Ford"; ms[47] = "BMW"; cout << ms[25] << endl; if (ms.count(47)) { cout << "Found an item with key 47 to be " << ms[47] << endl; for (const auto& pair: ms) cout << pair.first << " --> " << pair.second << ", "; cout << endl; 8

9 #include <stack> void teststack() { stack<int> st; st.push(25); st.push(47); assert(st.size() == 2); assert(st.top() == 47); st.pop(); assert(st.top() == 25); 9

10 How many Square's are created class Square { private: static int counter; public: Square() { cout << "Created " << ++counter << " Square" << endl; ; int Square::counter = 0; 1. Square s1; 2. Square mysquares[5]; 3. Square * mysquareptrs[5]; 4. vector<square> vsquare(10); 5. vector<square*> vsquareptrs(10); 10

11 How many Square's are created void test4() { vector<square> vsquare(10); void test5() { vector<square*> vsquareptrs(10); 11

12 priority queue (1) void testpq1() { priority_queue<int> pq; pq.push(27); pq.push(35); pq.push(5); // should get us while (!pq.empty()) { cout << pq.top() << " "; pq.pop(); cout << endl; 12

13 priority queue (2) void testpq2() { // use greater rather than less, // sorted from smallest to largest, default is less<string> priority_queue<string, vector<string>, greater<string>> pq; pq.push("apple"); pq.push("orange"); pq.push("banana"); // should get us apple banana orange while (!pq.empty()) { cout << pq.top() << " "; pq.pop(); cout << endl;; 13

14 priority queue (3) // new type integer-string pair // typedef pair<int, string> IntStr; using IntStr = pair<int, string>; void testpq3() { priority_queue<intstr> pq; pq.push(make_pair(27, "apple")); pq.push(make_pair(35, "orange")); pq.push(make_pair(5, "banana")); // should get us orange(35), apple(27), banana(5) while (!pq.empty()) { string str = pq.top().second; cout << str << "(" << pq.top().first << ")" << " "; pq.pop(); cout << endl;; What if we changed it to priority_queue<intstr, vector<intstr>, greater<intstr>> pq; 14

15 // store a pointer to a string and an integer pair // typedef pair<string *, int> StrptrInt; using StrptrInt = pair<string *, int>; // comparing StrptrInt objects based on the int value class StrptrIntCompare { // function object public: bool operator()(const StrptrInt &lhs, const StrptrInt &rhs) const return lhs.second > rhs.second; ; void testpq5() { priority_queue<strptrint,vector<strptrint>, StrptrIntCompare> pq; pq.push(make_pair(new string("apple"), 27)); pq.push(make_pair(new string("orange"), 35)); pq.push(make_pair(new string("banana"), 5)); // should get us banana(5) apple(27) orange(35) // when StrPintCompare is > while (!pq.empty()) { string *strptr = pq.top().first; cout << *strptr << "(" << pq.top().second << ")" << " "; delete pq.top().first; pq.pop(); cout << endl;; 15