ch 401 cpp include iostream h void main
- Slides: 81
/* 源文件名:ch 4_01. cpp 功能:取高分 */ #include <iostream. h> void main() { float score 1, score 2; cout << "请输入两个成绩:"; cin >> score 1 >> score 2; if (score 1 > score 2) { cout << score 1; } else 运行结果: { cout << score 2; } }
输入完成后,数据分别 存放在score 1和score 2 t=score 1 ; t score 1 73. 5 score 2 t score 1=score 2; 90 但不符题意,需要把2 变量数值交换一下,必 须定义中间变量t 任一随机数 90 t 73. 5 score 1 90 score 2=t; score 1 t 73. 5 90 score 2 73. 5
#include <iostream. h> #include <stdlib. h> #include <time. h> void main() { int obj, k; int num=0; srand(time(NULL)); obj=rand(); obj=obj%8+1; cout<<"有一个 1到 8之间的整数,请把它猜出来:"; outer: ; cin>>k; if (k==obj) { cout<<"成功!"<<endl; exit(0); } else { if (k>obj) cout<<"太大"<<endl; else { cout<<"太小"<<endl; } cout<<",请再猜!"; num+=1; if (num==3) { cout<<"失败!"; exit(0); } goto outer; } }
例:从键盘读入 1个整数,当数值为 1时,在屏幕输出 字符串“First”;当值为 2时,输出“Second”; 当值为 3时,输出“Third”; 其它值时输出“Other”. #include <iostream. h> void main( ) { int n; //若改为整型 char n; //注意不能是int型 case 2; case '2': cout << "Second"; break; case 3; case '3': cout << "Third"; break; cin >> n; default: switch (n) cout << "Other"; { } case 1; case ‘ 1’: //注意'1'是字符型 cout << "First"; break; }
若把break; 语句去掉,则运行结果如下: #include <iostream. h> void main( ) { char n; cin >> n; switch (n) { case '1': cout << "First"; case '2': cout << "Second"; case '3': cout << "Third"; default: cout << "Other"; } }
#include<iostream. h> void main() { char choice; cin >> choice; switch (choice) { case '0': cout << "Sunn"; break; case '1': cout << "Monn"; break; case '2': cout << "Tuen"; break; case '3': cout << "Wedn"; break; case '4': cout << "Thun"; break; case '5': cout << "Frin"; break; case '6': cout << "Satn"; break; default: cout << "输入错误"; } }
#include <iostream. h> void main() { int sum=0; int i; i = 1; do { sum = sum + i; i ++; } while (i <= 100); cout << sum << endl; }
以下写法可以使程序更简练 int sum=0; for(i=1; i<=100; i++) { sum += i; } cout <<sum<<endl; int sum=0; int i=1; while (i <= 100) { sum = sum + i++; } cout << sum << endl; int sum=0; int i=1; while (i <= 100) { sum += i++; } cout << sum << endl;
例:编写程序实现功能:求出 1到 100之间所有奇 数的和,并显示结果 int sum=0; int i=1; while (i <= 100) { if(i%2!=0) sum = sum + i; i++; } cout << sum << endl; int sum=0; for(i=1; i<=100; i++) { if(i%2!=0) sum = sum + i; } cout <<sum<<endl;
例:编写程序实现功能:求出 1到 100之间所有偶 数的和,并显示结果 int sum=0; int i=1; while (i <= 100) { if(i%2==0) sum = sum + i; i++; } cout << sum << endl; int sum=0; for(i=1; i<=100; i++) { if(i%2==0) sum = sum + i; } cout <<sum<<endl;
for语句可以将变量初始化部分加入其中 int sum=0; for(i=1; i<=100; i++) { if(i%2==0) sum = sum + i; } cout <<sum<<endl; for(i=1, sum=0; i<=100; i++) { if(i%2==0) sum = sum + i; } cout <<sum<<endl;
表达式 1与表达式 3均可无,但分号不可少 sum=0; for(i=1; i<=100; i++) { if(i%2==0) sum = sum + i; } cout <<sum<<endl; sum=0; int i=1; for( ; i<=100; ) { if(i%2==0) sum = sum + i; i++; } cout <<sum<<endl; for(表达式 1; 表达式 2; 表达式 3) 语句;
编程:计算并输出 1 -3+5 -7+-99+101的值 int s 1=0, s 2=0, i; for(i=1; i<=101; i+=4) s 1=s 1+i; for(i=-3; i>=-99; i+=-4) s 2=s 2+i; s 1=s 1+s 2; cout <<s 1<<endl; int s=0, t=1, i; for(i=1; i<=101; i+=2) { s = s + i*t; t = -t ; } cout <<s<<endl;
编 程 : 计 算 并 输 出 数 列 1– 1/3+1/5 -1/7+1/91/11+…+1/101的和 float s=0, t=1; int i; for(i=1; i<=101; i+=2) { s = s + 1 /( t * i ); t = -t ; } cout <<s<<endl;
编程:输出“九九表”,格式如下: 1 1 2 3 4 5 6 7 8 9 2 4 6 8 10 12 14 16 18 3 4 5 6 7 8 9 s = a × b a: 左起第一列 b: 顶端一行 9 12 15 18 21 24 27 16 20 24 28 32 36 25 30 35 40 40 36 42 48 54 49 56 63 64 72 81
int i, j; for(i=1; i<=4; i++) { for(j=1; j<=12 -2*i ; j++) cout<< " " ; for(j=1; j<=2*i-1; j++) cout<< "* " ; cout<< 'n'; } * * * * * * *
计 例: 100为止。 #include<iostream. h> #define pi 3. 14 void main() { int r; float area; for(r=1; r<=10; r++) { area=pi*r*r; if(area>100) break; cout<<area<<endl; } } 当计算值area>100时,执行 break语句,提前结束循环, 即不再继续执行其余的几 次循环
例:把100~200之间的不能被 3整除的数输出 #include <iostream. h> void main() { int n; for(n=100; n<=200; n++) {if(n%3==0) continue; cout<<n<<endl; } }
例:统计输入的字符串中,字符M的个数。 #include <iostream. h> void main() { char ch[100]; int i, sum=0; cout<<"input strings: "; cin>>ch; for(i=0; ch[i]!='