[명품 C++ Programming] 6장 실습 문제

1. int *y = NULL

#include <iostream>
using namespace std;

int add(int a[], int size) {
	int sum = 0;
	for (int i = 0; i < size; i++) {
		sum += a[i];
	}
	return sum;
}
int add(int a[], int size, int b[]) {
	return add(a, size) + add(b,size);
}

int main() {
	int a[] = { 1,2,3,4,5 };
	int b[] = { 6,7,8,9,10 };
	int c = add(a, 5);
	int d = add(a, 5, b);
	cout << c << endl;
	cout << d << endl;
}

#include <iostream>
using namespace std;

int add(int x[], int size,  int y[] = NULL) { // NULL 대신 nullptr로 하는 것이 바람직함
	int s = 0;
	for(int i=0; i<size; i++) // 배열 a의 합을 구한다.
		s += x[i];
	if(y == NULL) // NULL 대신 nullptr로 하는 것이 바람직함
		return s;

	for(int i=0; i<size; i++) // 배열 b를 합한다.
		s += y[i];
	return s;
}

int main() {
	int a[] = {1,2,3,4,5};
	int b[] = {6,7,8,9,10};
	int c = add(a, 5); // 배열 a의 정수를 모두 더한 값 리턴
	int d = add(a, 5, b); // 배열 a와 b의 정수를 모두 더한 값 리턴
	cout << c << endl; // 15 출력 
	cout << d << endl; // 55 출력
}

---

2.

#include <iostream>
#include <string>
using namespace std;


class Person {
	int id;
	double weight;
	string name;
public:
	void show() { cout << id << ' ' << weight << ' ' << name << endl;}
	Person(int id = 1, string naem = "Grace", double weight = 20.5);
};

Person::Person(int id, string name, double weight) {
	this->id = id;
	this->name = name;
	this->weight = weight;
}

int main() {
	Person grace, ashley(2, "Ashley"), helen(3, "Helen", 32.5);
	grace.show();
	ashley.show();
	helen.show();
}

---

3. 

(1)

#include <iostream>
#include <string>
using namespace std;


int big(int a, int b) {
	int n;
	n = a > b ? a : b;
	return n < 100?n:100;
}
int  big(int a, int b, int c) {
	int n = a > b ? a : b;
	return n > c ? c : n;
}

int main() {
	int x = big(3, 5);
	int y = big(300, 60);
	int z = big(30, 60, 50);
	cout << x << ' ' << y << ' ' << z << endl;
}

 

(2)

#include <iostream>
#include <string>
using namespace std;


int  big(int a, int b, int c = 100) {
	int n = a > b ? a : b;
	return n > c ? c : n;
}

int main() {
	int x = big(3, 5);
	int y = big(300, 60);
	int z = big(30, 60, 50);
	cout << x << ' ' << y << ' ' << z << endl;
}

---

4. 

#include <iostream>
#include <string>
using namespace std;


class MyVector {
	int* mem;
	int size;
public:
	MyVector(int val, int n = 100);
	~MyVector() { delete[] mem; }
};

MyVector::MyVector(int val, int n) {
	mem = new int[n];
	size = n;
	for (int i = 0; i < size; i++)
		mem[i] = 0;
}

int main() {

}

---

5. public: 유의 

#include <iostream>
#include <string>
using namespace std;

class ArrayUtility {
public:
	static void intToDouble(int source[], double dest[], int size);
	static void doubleToInt(double source[], int dest[], int size);
};

void ArrayUtility::intToDouble(int source[], double dest[], int size) {
	for (int i = 0; i < size; i++) {
		dest[i] = (double)source[i];
	}
}

void ArrayUtility::doubleToInt(double source[], int dest[], int size) {
	for (int i = 0; i < size; i++) {
		dest[i] = (int)source[i];
	}
}


int main() {
	int x[] = { 1,2,3,4,5 };
	double y[5];
	double z[] = { 9.9, 8.8, 7.7, 6.6,5.6 };

	ArrayUtility::intToDouble(x, y, 5);
	for (int i = 0; i < 5; i++) cout << y[i] << ' ';
	cout << endl;

	ArrayUtility::doubleToInt(z, x, 5);
	for (int i = 0; i < 5; i++) cout << x[i] << ' ';
	cout << endl;

}

---

7. (double)rand() / RAND_MAX

#include <iostream>
#include <string>
#include <cstdlib>
#include <ctime>
using namespace std;

class Random {
public:
	static void seed() { srand((unsigned)time(0)); }
	static int nextInt(int min = 0, int max = 32767);
	static char nextAlphabet();
	static double nextDouble();
};

int Random::nextInt(int min, int max) {
	return rand() % (max - min + 1) + min;
}

char Random::nextAlphabet() {
	int r =  rand() % 52;
	if (r < 26)
		return 'A' + r;
	else
		return 'a' + (r - 26);
}

double Random::nextDouble() {
	return (double)rand() / RAND_MAX;
}

int main() {
	Random::seed();

	cout << "1에서 100까지 랜덤한 정수 10개를 출력합니다." << endl;
	for (int i = 0; i < 10; i++) {
		cout << Random::nextInt(1, 100) << " ";
	}
	cout << endl;

	cout << "알파벳을 랜덤하게 10개를 출력합니다." << endl;
	for (int i = 0; i < 10; i++) {
		cout << Random::nextAlphabet() << " ";
	}
	cout << endl;

	cout << "랜덤한 실수를 10개 출력합니다." << endl;
	for (int i = 0; i < 10; i++) {
		cout << Random::nextDouble() << " ";
	}
	cout << endl;
}

 

---

9.  static 멤버 변수의 전역 변수 선언 /  클래스명::함수명() 호출

#include <iostream>
#include <string>
using namespace std;

class Board {
	static string post[100];
	static int index;
public:
	static void add(string s);
	static void print();
};

string Board::post[100];
int Board::index = 0;

void Board::add(string s) {
	if (index < 100)
		post[index++] = s;
}

void Board::print() {
	cout << "********** 게시판입니다. ************" << endl;
	for (int i = 0; i < index; i++) {
		cout << index << ": " << post[i] << endl;
	}
	
	index = 0;
}

int main() {
	Board::add("중간고사는 감독 없는 자율 시험입니다.");
	Board::add("코딩 라운지 많이 이용해주세요.");
	Board::print();
	Board::add("진소린 학생이 경진대회 입상하였습니다. 축하해주세요");
	Board::print();
}