運算符
算術運算符: 四則運算
賦值運算符: 將表達式的值賦給變量
比較運算符: 表達式的比較刊驴, 返回布爾值
邏輯運算符: 根據(jù)表達式的值返回真或者假
#include <iostream>
using namespace std;
// 運算符示例
int main() {
int a1 = 10;
int b1 = 3;
cout<< a1 + b1 << endl;
cout<< a1 - b1 << endl;
cout<< a1 * b1 << endl;
cout<< a1 / b1 << endl; // 兩個整數(shù)相除整除結(jié)果依然是整數(shù)
// 除數(shù)不能為 0
// b1 = 0;
// cout<<" a1 / b1 = "<< a1 / b1 << endl; // 會有錯誤
int a2 = 10;
int b2 = 20;
cout<< a2 / b2 << endl; // 0
// 小數(shù)相除
double d1 = 0.5;
double d2 = 0.25;
double res = d1/d2;
cout<<"d1/d2 = " <<res<< endl;
}
取模
#include <iostream>
using namespace std;
// 運算符示例 取模
int main() {
int a1 = 10;
int b1 = 3;
cout<< a1 % b1 << endl; // 1
// 除數(shù)不能為 0
// b1 = 0;
// cout<<" a1 / b1 = "<< a1 / b1 << endl; // 會有錯誤
// 取模除數(shù)也不能為0
int a2 = 10;
int b2 = 20;
cout<< a2 % b2 << endl; // 10
// 小數(shù)不能取模
// double d1 = 0.5;
// double d2 = 0.25;
// double res = d1%d2;
// cout<<"d1/d2 = " <<res<< endl;
}
自增運算
#include <iostream>
using namespace std;
// 自增運算符
int main() {
// 后置遞增
int a = 10;
a++; // 等價于 a = a + 1
cout << "a = " << a << endl;
// 前置遞增
int b = 10;
++b; //
cout << "b = " << b << endl;
// 區(qū)別
// 前置遞增是先對變量進行++涧至, 然后再參與計算表達式
int a2 = 10;
int b2 = ++a2*10;
cout << "b2 = " << b2 << endl;
cout << "a2 = " << a2 << endl;
// 后置遞增是先參與計算表達式芥永, 然后再對變量進行++
int a3 = 10;
int b3 = a3++*10;
cout << "b3 = " << b3 << endl;
cout << "a3 = " << a3 << endl;
}
賦值運算符
#include <iostream>
using namespace std;
// 賦值運算符
int main() {
//
int a = 10;
cout << "a = " << a << endl;
a = 100;
a += 2; // a = a + 2
cout << "a = " << a << endl;
a -= 2;
cout << "a = " << a << endl;
a *= 2;
cout << "a = " << a << endl;
a /= 2;
cout << "a = " << a << endl;
a %= 2;
cout << "a = " << a << endl;
}
比較運算符
#include <iostream>
using namespace std;
// 比較運算符
int main() {
int a = 10;
int b = 20;
cout <<(a == b) << endl; // 0 false
cout <<(a != b) << endl; // 1 true
cout <<(a > b) << endl; // 0 false
cout <<(a < b) << endl; // 1 true
cout <<(a <= b) << endl; // 1 true
cout <<(a >= b) << endl; // 0 false
int res = (a == b);
cout <<"res = "<< res << endl; // 0 false
bool flag = (a == b);
cout <<"flag = "<< flag << endl; // flag = 0
// 在c++/c 中比較運算 真 用 1 表示 假用 0 表示
}
邏輯運算符
#include <iostream>
using namespace std;
// 邏輯運算符
int main() {
// 非
int a = 100;
cout << !a << endl; // 0
cout << !!a << endl; // 1
// 與
int b = 10;
int c = 10;
cout << (b && c) << endl; // 1
// 或
int d = 0;
cout << (d || c) << endl; // 1
}
程序流程結(jié)構(gòu)
C/C++?持最基本的三種程序運?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?哀蘑,有選擇的執(zhí)?相應功能
- 循環(huán)結(jié)構(gòu):依據(jù)條件是否滿?,循環(huán)多次執(zhí)?某段代碼
選擇結(jié)構(gòu)
單行if
if(條件){
條件為真時執(zhí)行的事情
}
栗子1
#include <iostream>
using namespace std;
// 選擇結(jié)構(gòu)
int main() {
int score;
cout<< "please input your score"<< endl;
cin >> score;
cout<< "your score is "<< score<< endl;
if (score >= 600){
cout<< "your score is very good "<< endl;
}
}
if(條件){
條件為真時執(zhí)行的事情
}else{
不滿足條件為真時執(zhí)行的事情
}
#include <iostream>
using namespace std;
// 成績level顯示器
int main() {
int score;
cout<< "please input your score"<< endl;
cin >> score;
cout<< "your score is "<< score<< endl;
if (score >= 90 && score <= 100){
cout<< "your score level is A "<< endl;
}else if (score >= 80 && score < 90){
cout<< "your score level is B "<< endl;
}else if (score >= 60 && score < 80){
cout<< "your score level is C "<< endl;
}else if (score >= 0 && score < 60){
cout<< "your score level is D "<< endl;
}else{
cout<< "your score is error "<< endl;
}
}
作業(yè)1:三只小豬稱重
有三只?豬ABC葵第,請分別輸?三只?豬的體重递礼,并且判斷哪只?豬最重?
#include <iostream>
using namespace std;
int main() {
int pigA;
int pigB;
int pigC;
cout<< "please input your score"<< endl;
cin >> pigA;
cin >> pigB;
cin >> pigC;
cout<< "pigA"<<pigA<< endl;
cout<< "pigB"<<pigB<< endl;
cout<< "pigC"<<pigC<< endl;
}
作業(yè)2:BMI計算器
計算公式為:BMI=體重÷身高2羹幸。(體重單位:千克脊髓;身高單位:米。)