C++面向对象程序设计 笔记整理——编程基础

字符与字符串

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 大小写转换

void lower_or_upper_case(char c){ int transferred_c; if ( ('a'<=c) && (c<='z') ) {  transferred_c = (int)c - ( (int)'b' - (int)'B' );  cout << "The lower/upper case is: " << (char)transferred_c << endl; } else if ( ('A'<=c) && (c<='Z') ) {  transferred_c = (int)c + ( (int)'a' - (int)'A' );  cout << "The lower/upper case is: " << (char)transferred_c << endl; } else  cout << "您输入的不是字母" << endl; }int main(){ char letter; cout << "Please enter a letter: "; cin >> letter; lower_or_upper_case(letter); char c = 'A';  cout << c << endl;}

 

程序的控制结构

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例题0: 鸡兔同笼

鸡、兔共有98个头，386只脚，求鸡、兔各多少只。 使用遍历方法求所有解

int main(){ for (int i = 0; i <= 98; i++) // i: chicken {  int j = 98 - i; // j: rabbit  if ((2*i + 4*j) == 386)  {   cout << "chicken: " << i << " rabbit: " << j << endl;  } } return 0;}

例题1:

π/4 = 1 - 1/3 + 1/5 - 1/7 + ... 直到最后一项的绝对值小于10^-6为止

int main(){ double sum = 0; double temp = 1; int i = 1; while (abs(temp) >= 1e-6) {  temp = pow(-1.0, i+1) / (2*i -1);  cout << fixed << setprecision(0) << pow(-1.0, i+1) << "/" << (2*i -1) << ": ";  cout << scientific << setprecision(1) << temp << endl;  i++;  sum += temp; } cout << endl; cout << sum << endl; system("pause"); return 0;}

例题2: 阶乘数列求和

S = 1!+2!+...+n!

int factorial(int k) //阶乘函数{ int product = 1; for (int i = 1; i <=k; i++)  product *= i; return product;}int main(){ int sum = 0, n; cout << "please enter a number: "; cin >> n; for (int i=1; i<=n; i++) {  sum += factorial(i); } cout << "The result is: " << sum << endl; return 0;}

例题3: 菲波那切数列

S = 1+1+2+3+5+8+13+21+...

int sum_fibonacci_sequence(){ static int a = 0, b = 1; int t = a; a = b; b = t + b; //cout << a << " " << b << endl; return a;}int main(){ int result = 0, n; cout << "please enter n: "; cin >> n; for (int i = 1; i <= n; i++) {  int an = sum_fibonacci_sequence();  result += an;  cout << "an is: " << an << endl; } cout << result << endl; return 0;}

 

指针

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使用指针动态生成数组

 int length; cout << "input x length: "; cin >> length; int* a; a = new int[length]; a[0] = 25; cout << a[0] << endl; delete[] a;  // 释放内存

 

递归

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使用递归来计算阶乘

long factorial(long n){ cout << "cur n == " << n << endl; if (n < 0)  return -1; else if (n == 0 || n == 1) // 函数终止条件, 小事化了  return 1; else {  long ret;  ret = n * factorial(n-1);  cout << "cur ret == " << ret << endl;  return ret; // 大事化小, 调用自身进行递归, 想办法把表达式变成 f(n) = g( f(n-1) , n ) }}

 

常用模块

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向量 vector

#include <vector>int main(){ vector<int> x; x.push_back(1); x.push_back(2); int y = 345; x.push_back(y);　　// 动态插入成员 cout << x.size() << endl;　　// 获取长度 x.pop_back();  // 删除最后一个成员 for (int k=0; k<x.size(); k++) {  cout << x[k] << endl; } return 0;}

 

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字符与字符串大小写转换voidlower_or_upper_case(charc){inttransferred_c;if(('a'<=c)&&(c<='z')){transferred_c=(int)c-((int)'b'-(int)'B');cout<<"Thelower/uppe
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