運(yùn)算符
算術(shù)運(yùn)算符： 四則運(yùn)算
賦值運(yùn)算符： 將表達(dá)式的值賦給變量
比較運(yùn)算符： 表達(dá)式的比較， 返回布爾值
邏輯運(yùn)算符： 根據(jù)表達(dá)式的值返回真或者假
算術(shù)運(yùn)算符
#include <iostream>
using namespace std;
int main(){
int a = 10;
int b = 3;
double c = 3;
cout << "a + b = "<< a + b << endl;
cout << "a - b = "<< a - b << endl;
cout << "a x b = "<< a * b << endl;
cout << "a / b = "<< a / b << endl; // 整除
cout << "a / c = "<< a / c << endl; // 整除
cout << "a % b = "<< a % b << endl;
// cout << "a % c = "<< a % c << endl; // 小數(shù)不能取模
}
#include <iostream>
using namespace std;
int main(){
int a = 10;
// 共同點(diǎn) 都是自增一次
// a++;
// cout<<a<< endl; //11
// ++a;
// cout <<a <<endl; //12
// 不同:
// 前置++是先自增,再參與運(yùn)算
// 后置++是先參與運(yùn)算,再自增
int b = 3;
int c = a++*3 + b;
cout << c <<endl; //33
int d = ++a*3 + b;
cout << d <<endl; //39
cout << a++ <<endl; // 12
cout << ++a <<endl; // 14
}
賦值運(yùn)算符
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#include <iostream>
using namespace std;
int main(){
int age = 18;
// age = age + 20;
age += 20;
cout <<age<< endl;
int b = 10;
b*=3;
cout <<b<< endl;
}
比較運(yùn)算符
image
#include <iostream>
using namespace std;
int main(){
// int a = 10;
// int b = 10;
int a;
int b;
cout << "please input a "<<endl;
cin >>a;
cout << "please input b "<<endl;
cin >>b;
cout << "a == b "<< (a==b) <<endl; // 1 true
cout << "a != b "<< (a!=b) <<endl; // 0 fasle
cout << "a <= b "<< (a<=b) <<endl;
cout << "a < b "<< (a<b) <<endl;
cout << "a >= b "<< (a>=b) <<endl;
cout << "a > b " << (a>b) <<endl;
}
邏輯運(yùn)算符
#include <iostream>
using namespace std;
int main(){
int a = 10;
// 非
bool res1 = !a;
cout <<res1 <<endl;
cout <<!!a <<endl;
// 與 同真為真
int b = 11;
int c = 12;
cout << (a < b && a < c) <<endl; // 1
cout << (a > b && a < c) <<endl; // 0
// 或 有一個(gè)為真就是真
cout << (a < b || a < c) <<endl; // 1
cout << (a > b || a < c) <<endl; // 1
cout << (a > b || a > c) <<endl; // 0
}
程序流程結(jié)構(gòu)
C/C++?持最基本的三種程序運(yùn)?結(jié)構(gòu)：順序結(jié)構(gòu)、選擇結(jié)構(gòu)、循環(huán)結(jié)構(gòu)
- 順序結(jié)構(gòu)：程序按順序執(zhí)?，不發(fā)?跳轉(zhuǎn)
- 選擇結(jié)構(gòu)：依據(jù)條件是否滿(mǎn)?，有選擇的執(zhí)?相應(yīng)功能
- 循環(huán)結(jié)構(gòu)：依據(jù)條件是否滿(mǎn)?，循環(huán)多次執(zhí)?某段代碼
選擇結(jié)構(gòu)
單行if
if(條件){
條件為真時(shí)執(zhí)行的事情
}
#include <iostream>
using namespace std;
int main(){
int age;
cout << "please input your age"<<endl;
cin >> age;
if (age >= 18){
cout << "cheng nian"<<endl;
}
}
if(條件){
條件為真時(shí)執(zhí)行的事情
}else{
不滿(mǎn)足條件為真時(shí)執(zhí)行的事情
}
#include <iostream>
using namespace std;
int main(){
int age;
cout << "please input your age"<<endl;
cin >> age;
if (age >= 18){
cout << "cheng nian"<<endl;
}else{
cout << "bao bao "<<endl;
}
}
多重判斷
#include <iostream>
using namespace std;
int main(){
int score;
cout << "please input your score"<<endl;
cin >> score;
// if else if else 下面只有一行語(yǔ)句的時(shí)候可以省略大括號(hào)
if (score >= 90 && score <= 100)
cout << "A level"<<endl;
else if (score >= 75 && score < 90)
cout << "B level"<<endl;
else if (score >= 60 && score < 75)
cout << "C level"<<endl;
else if (score >= 0 && score < 65)
cout << "D level"<<endl;
else
cout << "data error"<<endl;
}
三只小豬稱(chēng)重
有三只?豬ABC，請(qǐng)分別輸?三只?豬的體重，并且判斷哪只?豬最重？
image
#include <iostream>
using namespace std;
int main(){
double pigA;
cout << "please input pigA weight"<<endl;
cin >> pigA;
double pigB;
cout << "please input pigB weight"<<endl;
cin >> pigB;
double pigC;
cout << "please input pigC weight"<<endl;
cin >> pigC;
double maxWeight;
// if (pigA > pigB)
// maxWeight = pigA;
// else
// maxWeight = pigB;
// if (maxWeight < pigC)
// maxWeight = pigC;
// cout << "the most weighted"<<maxWeight<<endl;
if (pigA > pigB){
if (pigA > pigC){
cout << "pigA = "<<pigA<<endl;
} else{
cout << "pigC = "<<pigC<<endl;
}
} else{
if (pigB > pigC){
cout << "pigB = "<<pigB<<endl;
} else{
cout << "pigC = "<<pigC<<endl;
}
}
}
BMI計(jì)算器
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計(jì)算公式為：BMI=體重÷身高^(guò)2。（體重單位：千克；身高單位：米。）
pwd 當(dāng)前目錄
cd 切換目錄
./文件名執(zhí)行文件
