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[数据结构与算法]C++学习笔记

目录

冒泡排序

void Bubble_Sort(int* const array, int array_size) {
	for (int i = 1; i < array_size; i++)
	{
		for (int j = 0; j < array_size - i; j++)
		{
			if (array[j] > array[j + 1])
			{
				int temp = array[j];
				array[j] = array[j + 1];
				array[j + 1] = temp;
			}
		}
	}
}

九九乘法表

#include<iostream>
using namespace std;

int main() {
	
	for (int i = 1; i < 10; i++) {
		for (int j = 1; j <=i; j++) {
		
			cout << j << "*" << i << "=" << i * j << "\t";
		}
		cout <<"\n" << endl;
	}

	system("pause");
	return 0;
}

水仙花数

#include<iostream>
#include<math.h>
using namespace std;

int main() {
	
	int a = 0, b = 0, c = 0;
	for (int i = 100; i < 1000; i++){
		a = i / 100;//百位
		b = i / 10 % 10;//十位
		c=i % 10;//个位
		if (pow(a, 3) + pow(b, 3) + pow(c, 3) == i) {
			cout << "水仙花数: " << i << endl;
		}
	}

	system("pause");
	return 0;
}

猜数字

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

int main() {
	srand((unsigned int)time(NULL));//随机数种子
	int num = rand() % 100 + 1;//生成1~100的一个随机数
	int value;

	while (num) {
		cout << "输入一个数: ";
		cin >> value;

		if (value > num) {
			cout << "猜大了" << endl;
		}
		else if(value < num){
			cout << "猜小了" << endl;
		}
		else {
			cout << "猜对了!" << endl;
			break;
		}
	}

	system("pause");
	return 0;
}

时间戳

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

int main() {

	cout << "时间戳: " << (unsigned int)time(NULL) << endl;

	system("pause");
	return 0;
}

7的倍数,含有7就拍桌子

#include<iostream>
using namespace std;

int main() {

	for (int i = 1; i <= 100; i++) {
		/*
		!(i%7)//7的倍数
		i/10==7//十位上有7
		i%10==7//个位上有7
		*/
		if (!(i % 7) || i / 10 == 7 || i % 10 == 7) {
			cout << "拍桌子(" << i << ")" << endl;
		}
		else {
			cout << i << endl;
		}
	}

	system("pause");
	return 0;
}

goto

#include<iostream>
using namespace std;

int main() {

	cout << "1.XXXXXX" << endl;

	cout << "2.XXXXXX" << endl;
	goto FLAG;
	cout << "3.XXXXXX" << endl;

	cout << "4.XXXXXX" << endl;
	FLAG:
	cout << "5.XXXXXX" << endl;

	system("pause");
	return 0;
}

数组名

#include<iostream>
using namespace std;

int main() {

	int arr[] = { 1,2,3,4,5,6,7,8,9,10 };

	cout << "数组在内存中的首地址(十六进制): " << arr << endl;
	cout << "数组在内存中的首地址(十进制): " << (int)arr << endl;
	cout << "数组中的第一个元素在内存中的地址(十进制): " << (int)&arr[0] << endl;
	cout << "数组占用的内存空间: : " << sizeof(arr) << endl;
	cout << "数组中每个元素占用的内存空间 : " << sizeof(arr[0]) << endl;
	cout << "数组元素的个数 : " << sizeof(arr)/sizeof(arr[0]) << endl;

	system("pause");
	return 0;
}

最大值

#include<iostream>
using namespace std;

int main() {
	
	int arr[] = { 300,350,200,400,250 }, max = 0;

	for (int i = 0; i < sizeof(arr) / sizeof(arr[0]); i++) {
		max = arr[i] > max ? arr[i] : max;
	}
	cout << "数组中最大值: " << max << endl;

	system("pause");
	return 0;
}

数组逆序

#include<iostream>
using namespace std;

int main() {
	
	int arr[] = { 1,3,2,5,4,6,2}, temp = 0;

	int num = sizeof(arr) / sizeof(arr[0]) - 1;//数组最后一个元素索引

	for (int i = 0; i <= num/2; i++) {
		temp = arr[i];
		arr[i] = arr[num - i];
		arr[num - i] = temp;
	}

	for (int i = 0; i <= num; i++) {
		cout << arr[i] << endl;
	}

	system("pause");
	return 0;
}

二维数组的数组名

#include<iostream>
using namespace std;

int main() {

	int arr[][3] = {
		{1,2,3},
		{4,5,6}
	};

	cout << "数组大小 " << sizeof(arr) << endl;
	cout << "二维数组第一行大小 " << sizeof(arr[0]) << endl;
	cout << "二维数组元素大小 " << sizeof(arr[0][0]) << endl;

	cout << "二维数组行数 " << sizeof(arr)/ sizeof(arr[0]) << endl;
	cout << "二维数组列数 " << sizeof(arr[0]) / sizeof(arr[0][0]) << endl;

	cout << "二维数组首地址 " << (int)arr << endl;
	cout << "二维数组第一行首地址 " << (int)arr[0] << endl;
	cout << "二维数组第二行首地址 " << (int)arr[1] << endl;

	cout << "二维数组第一个元素首地址 " << (int)&arr[0][0] << endl;
	cout << "二维数组第二个元素首地址 " << (int)&arr[0][1] << endl;
	system("pause");
	return 0;
}

成绩求和

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

int main() {

	int arr[][3] = {
		{100,100,100},
		{90,50,100},
		{60,70,80}
	};
	
	string name[3] = { "张三","李四","王五" };

	int raw = sizeof(arr) / sizeof(arr[0]);
	int col = sizeof(arr[0]) / sizeof(arr[0][0]);

	for (int i = 0; i < raw; i++) {
		
		int sum = 0;
		for (int j = 0; j < col; j++) {
		
			sum += arr[i][j];
		}
		cout << name[i]  << "的总成绩: " << sum << endl;
	}

	system("pause");
	return 0;
}

两数相加函数

#include<iostream>
using namespace std;

int add(int num1, int num2) {

	return num1 + num2;
}

int main() {

	cout << add(1, 3) << endl;

	system("pause");
	return 0;
}

值传递,形参发生任何改变,都不会影响实参

#include<iostream>
using namespace std;

void swap(int num1, int num2) {

	cout << "交换前" << endl;
	cout << "num1= " << num1 << endl;
	cout << "num2= " << num2 << endl;

	int temp = num1;
	num1 = num2;
	num2 = temp;

	cout << "交换后" << endl;
	cout << "num1= " << num1 << endl;
	cout << "num2= " << num2 << endl;
}

int main() {

	int a = 10, b = 20;

	cout << "a= " << a << endl;
	cout << "b " << b << endl;

	swap(a, b);

	cout << "a= " << a << endl;
	cout << "b " << b << endl;

	system("pause");
	return 0;
}

函数的定义

#include<iostream>
using namespace std;

//在main()之前定义
int max(int num1, int num2) {
	return num1 > num2 ? num1 : num2;
}

int main() {

	cout << max(10, 20) << endl;

	system("pause");
	return 0;
}

函数的声明和定义

#include<iostream>
using namespace std;

//在main()之前声明
int max(int num1, int num2);

int main() {

	cout << max(10, 20) << endl;

	system("pause");
	return 0;
}

//在main()之后定义
int max(int num1, int num2) {
	return num1 > num2 ? num1 : num2;
}

函数的分文件编写

  1. 创建.h的头文件
  2. 创建.cpp的源文件
  3. 在头文件中写函数声明
  4. 在源文件中写函数的定义
//swap.h
#pragma once
#include<iostream>
using namespace std;

void swap(int a, int b);

//swap.cpp
#include "swap.h"

void swap(int a, int b) {

	int temp = a;
	a = b;
	b = temp;

	cout << "a= " << a << endl;
	cout << "b= " << b << endl;
}

//source.cpp
#include<iostream>
using namespace std;
#include "swap.h"


int main() {

	swap(10, 20);

	system("pause");
	return 0;
}

指针的定义和使用

#include<iostream>
using namespace std;

int main() {

	int a = 10;
	//1.定义指针
	int* p = &a;
	cout << "a的地址: " << &a << endl;
	cout << "指针p为: " << p << endl;

	//2.使用指针
	*p = 100;
	cout << "a= " << a << endl;
	cout << "*p= " << *p << endl;

	system("pause");
	return 0;
}

指针所占内存空间

#include<iostream>
using namespace std;

int main() {

	int a = 10;
	int* p = &a;

	cout << "a= " << *p << endl;
	cout << "p " << sizeof(p) << endl;//指针所占内存空间
	cout << "*p " << sizeof(*p) << endl;//数据所占内存空间
	cout << "char* " << sizeof(char*) << endl;
	cout << "float* " << sizeof(float*) << endl;
	cout << "double* " << sizeof(double*) << endl;

	system("pause");
	return 0;
}

空指针

#include<iostream>
using namespace std;

int main() {

	int* p = NULL;//空指针

	system("pause");
	return 0;
}

野指针

#include<iostream>
using namespace std;

int main() {
	//野指针
	//int* p = (int*)0x1100;//错误

	system("pause");
	return 0;
}

const 修饰指针

#include<iostream>
using namespace std;

int main() {
	//const修饰的值不能改

	int a = 10, b = 20;
	//1.常量指针
	const int* p1 = &a;
	p1 = &b;//正确

	//2.指针常量
	int* const p2 = &b;
	*p2 = a;

	//3.const 修饰指针和常量
	const int* const p3 = &a;

	system("pause");
	return 0;
}

指针和数组

#include<iostream>
using namespace std;

int main() {
	
	int arr[] = { 1,2,3,4,5,6,7,8,9,10 };

	int* p = arr;

	cout << "第一个元素 " << arr[0] << endl;
	cout << "指针访问第一个元素 " << *p << endl;

	for (int i = 0; i < sizeof(arr) / sizeof(arr[0]); i++, p++) {
	
		cout << *p << endl;
	}

	system("pause");
	return 0;
}

值传递和地址传递

#include<iostream>
using namespace std;

//值传递
void swap01(int a, int b) {

	int temp = a;
	a = b;
	b = temp;
}

//地址传递
void swap02(int* p1, int* p2) {

	int temp = *p1;
	*p1 = *p2;
	*p2 = temp;
}

int main() {
	int a = 10, b = 20;
	cout << "a= " << a << endl;
	cout << "b= " << b << endl;

	cout << "值传递" << endl;
	swap01(a, b);
	cout << "a= " << a << endl;
	cout << "b= " << b << endl;

	cout << "地址传递" << endl;
	swap02(&a, &b);
	cout << "a= " << a << endl;
	cout << "b= " << b << endl;

	system("pause");
	return 0;
}

指针配合数组和函数

#include<iostream>
using namespace std;

void bubleSort(int* arr, int len) {
	
	for (int i = 0; i < len; i++) {
	
		for (int j = 0; j < len - i - 1; j++) {
		
			if (arr[j] > arr[j + 1]) {
			
				int temp = arr[j];
				arr[j] = arr[j + 1];
				arr[j + 1] = temp;
			}
		}
	}
}

int main() {

	int arr[] = {4,3,6,9,1,2,10,8,7,5};
	int len = sizeof(arr) / sizeof(arr[0]);

	bubleSort(arr, len);

	for (int i = 0; i < len; i++) {
	
		cout << arr[i] << "\t";
		
	}
	cout <<endl;

	system("pause");
	return 0;
}

结构体定义和使用

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

struct Student {
	string name;
	int age;
	int score;
};

int main() {
	
	Student s1;
	s1.name = "张三";
	s1.age = 18;
	s1.score = 60;

	Student s2 = { "李四",19,70 };

	cout << "姓名: " << s2.name 
		 << " 年龄: " << s2.age 
		 << " 成绩: " << s2.score << endl;

	system("pause");
	return 0;
}

结构体数组

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

struct Student {
	string name;
	int age;
	int score;
};

int main() {
	
	Student stuArray[3] = {
		{"张三",18,60},
		{"李四",19,70},
		{"王五",20,80}
	};

	for (int i = 0; i < 3; i++) {
		cout << "姓名: " << stuArray[i].name
			 << " 年龄: " << stuArray[i].age
			 << " 成绩: " << stuArray[i].score << endl;
	}

	system("pause");
	return 0;
}

结构体指针

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

struct Student {
	string name;
	int age;
	int score;
};

int main() {
	
	Student s1 = {"张三",18,60};
	cout << "姓名: " << s1.name
		<< " 年龄: " << s1.age
		<< " 分数: " << s1.score << endl;
	
	Student* p = &s1;
	cout << "姓名: " << p->name
		<< " 年龄: " << p->age
		<< " 分数: " << p->score << endl;

	system("pause");
	return 0;
}

结构体嵌套结构体

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

struct Student {
	string name;
	int age;
	int score;
};

struct Teacher {
	int id;
	string name;
	int age;
	Student stuArray[2];
};

int main() {
	Teacher t;
	t.name = "老王";
	t.id = 001;
	t.age = 50;

	t.stuArray[0].name = "张三";
	t.stuArray[0].age = 18;
	t.stuArray[0].score = 60;

	t.stuArray[1].name = "李四";
	t.stuArray[1].age = 19;
	t.stuArray[1].score = 70;

	system("pause");
	return 0;
}

结构体做函数参数

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

struct Student {
	string name;
	int age;
	int score;
};

void print1(Student stu) {
	cout << "值传递打印 " << " 姓名: " << stu.name
		<< " 年龄: " << stu.age
		<< " 分数: " << stu.score << endl;
};

void print2(Student* p) {
	p->name = "李四";
	cout << "地址传递打印 " << " 姓名: " << p->name
		<< " 年龄: " << p->age
		<< " 分数: " << p->score << endl;
};

int main() {
	
	Student s = { "张三",18,60 };
	cout << "main函数中打印 " << " 姓名: " << s.name
		<< " 年龄: " << s.age
		<< " 分数: " << s.score << endl;

	print1(s);
	print2(&s);

	system("pause");
	return 0;
}

结构体中const的使用场景

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

struct Student {
	string name;
	int age;
	int score;
};

void print1(const Student* p) {
	cout << "地址传递打印 " << " 姓名: " << p->name
		<< " 年龄: " << p->age
		<< " 分数: " << p->score << endl;
};

int main() {
	
	Student s = { "张三",18,60 };
	cout << "main函数中打印 " << " 姓名: " << s.name
		<< " 年龄: " << s.age
		<< " 分数: " << s.score << endl;

	print1(&s);

	system("pause");
	return 0;
}

结构体案例1

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

struct Student {
	string sName;
	int score;
};

struct Teacher
{
	string tName;
	Student sArray[5];
};

void allocatespace(Teacher tArray[], int len) {
	string nameSeed = "ABCDE";
	for (int i = 0; i < len; i++) {
		tArray[i].tName = "teacher_";
		tArray[i].tName += nameSeed[i];
		for (int j = 0; j < 5; j++) {
			tArray[i].sArray[j].sName = "student_";
			tArray[i].sArray[j].sName += nameSeed[j];

			int random = 60 + rand() % 41;
			tArray[i].sArray[j].score = random;
		}
	}
};

void printinfo( Teacher tArray[],int len) {
	for (int i = 0; i < len; i++) {
		cout << "老师姓名: " << tArray[i].tName << endl;
		for (int j = 0; j < 5; j++) {
			cout << "\t学生姓名: " << tArray[i].sArray[j].sName
				<< " 得分: " << tArray[i].sArray[j].score << endl;
		}
	}
};

int main() {
	
	srand((unsigned int)time(NULL));

	Teacher tArray[3];
	int len = sizeof(tArray) / sizeof(tArray[0]);
	allocatespace(tArray, len);

	printinfo(tArray, len);
	system("pause");
	return 0;
}

结构体案例2

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

struct Hero {

	string name;
	int age;
	string sex;
};

void bubbleSorrt(Hero HeroArray[], int len) {
	for (int i = 0; i < len - 1; i++) {
		for (int j = 0; j < len - 1 - i; j++) {
			if (HeroArray[j].age > HeroArray[j + 1].age) {
				Hero temp = HeroArray[j];
				HeroArray[j] = HeroArray[j + 1];
				HeroArray[j + 1] = temp;
			}
		}
	}
};

void printinfo(Hero HeroArray[], int len) {
	for (int i = 0; i < len; i++) {
		cout << HeroArray[i].name << "\t"
			<< HeroArray[i].age << "\t"
			<< HeroArray[i].sex << endl;
	}
};

int main() {
	
	Hero HeroArray[5] = {
		{"刘备",23,"男"},
		{"关羽",22,"男"},
		{"张飞",20,"男"},
		{"赵云",21,"男"},
		{"貂蝉",19,"男"}
	};

	int len = sizeof(HeroArray) / sizeof(HeroArray[0]);
	cout << "\t排序前" << endl;
	printinfo(HeroArray, len);
	
	bubbleSorrt(HeroArray, len);

	cout << "\t排序后" << endl;
	printinfo(HeroArray, len);

	system("pause");
	return 0;
}

MPI并行——梯形积分

#include<iostream>
#include<math.h>
#include "mpi.h"
using namespace std;

double f(double x) {
	return x*x*x;
}

double trap(double a, double b, int n) {

	double h = (b - a) / n;
	double sum = (f(a) + f(b)) / 2;
	for (int i = 1; i < n; i++)
	{
		sum += f(a + i * h);
	}
	return sum * h;
}

int main(void) {
	int n = 9000;
	double a = -2, b = 2;

	int rank, comm_sz;
	MPI_Status status;
	MPI_Init(NULL, NULL);
	MPI_Comm_rank(MPI_COMM_WORLD, &rank);
	MPI_Comm_size(MPI_COMM_WORLD, &comm_sz);

	int local_n = n / comm_sz;
	double local_width = (b - a) / comm_sz;
	double local_a = a + rank * local_width;
	double local_b = local_a + local_width;

	double local_sum = trap(local_a, local_b, local_n);

	double cacha_sum;

	MPI_Reduce(&local_sum, &cacha_sum, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD);
	if (rank == 0) {
		cout << "With n = " << n << " trapeziods, our estimate" << endl;
		cout << "of the integral from " << a << " to " << b << " = " << cacha_sum << endl;
	}
	MPI_Finalize();
	return 0;
}

With n = 9000 trapeziods, our estimate
of the integral from -2 to 2 = -8.88178e-16
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