C语言课后习题答案

第4章后练习10. ch4_lx10.c#include <stdio.h>void main(){int m=1,n=1,s=0,k=1;while(n<=10){while(m<=n){printf("%d",m);m++;}printf("\n");n++;m=1;}}Ch4_lx12.c 输入一行字符串,统计有多少字母.#include <stdio.h>void main(){int m=0;char ch;while( (ch=getchar() )!='\n')if((ch>='a'&&ch<='z')||(ch>='A'&&ch<='Z'))m++;printf("%d\n",m);}}Ch4_lx13.c 猜字游戏#include<stdio.h>#include<stdlib.h>#include<math.h>#include<time.h>void main( ){ int magic ;int guess;srand( (unsigned) time(NULL) );magic=rand();printf("Enter your guess:");scanf("%d",&guess);while( guess!=magic){if(guess>magic)printf(" ** Too high\n**");elseprintf(" ** Too Low\n**");printf("Enter your guess:");scanf("%d",&guess);if(guess ==magic){ printf("**Right**\n");break;}}}11. 输入一自然数，输出它的因子。

解1.#include<stdio.h>int main(){ int w,i=2;printf("请输入一个整数w: \n");scanf("%d",&w);printf("%d的因子是:",w); while(w){ while(w){if(w%i==0){ printf(" %d ",i);w=w/i;}elsebreak;}i++;}return 0;}Ch5_lx14.c 求1*3*5*7…*n#include<stdio.h>int main(){int i,x,s=1;printf("请输入一个奇数:\n");scanf("%d",&x);for(i=1;i<=x;i+=2)s=s*i;printf("1*3*...*%d=%d\n",x,s);return 0;}设计一个猜字游戏.程序给出一个数,游戏者猜对了,屏幕显示“**Right**”;当猜的数错了,显示”**Wrong**”,并告之猜的数太小并显示” ** Too Low**”,否则就显示”**Too High**”.例:猜字游戏(一)main( ){ int magic =123;int guess;printf(“Enter your guess:”;scanf(“%d”,&guess);if(guess ==magic)printf(“**Right**”);else{ printf(“ ** Wrong**”);if(guess>magic)printf(“ ** Too high\n**”);elseprintf(“ ** Too low **\n”);}}main( ) 猜字游戏(二){ int magic =123;int guess;printf("Enter your guess:");scanf("%d",&guess);while(guess!=magic){ if(guess ==magic)printf("**Right**\n");else{ printf(" ** Wrong**\n");if(guess>magic)printf(" ** Too high\n**");elseprintf(" ** Too Low\n**");}printf("Enter your guess:");scanf("%d",&guess); } }例:一球从100米高度自由落下,每次落地后都弹回原高度一半落下，求它在第10次落地时, 共经过多少米？第10次反弹多高？main(){ float sn=100,hn=sn/2;int n;for(n=2;n<=10;n++){ sn=sn+2*hn;hn=hn/2; }printf(“%f m.\n”,sn);printf(“%f m.\n”,hn); }例: 猴子吃桃子问题.猴子第一天摘下若干桃子,当即吃了一半,又多吃了一个. 第二天早上又将剩余的桃子吃掉一半,还是又多吃了一个.以后每天早上都吃了前天剩下的一半多一个. 到第十天早上想再吃时,只见剩下了一个桃子了.求第一天共摘了多少桃子?main(){int day,x1,x2;day=9;x2=1;while(day>0){x1=(x2+1)*2;x2=x1;day--;}printf(“total=%d\n”,x1);}12. #include <stdio.h>void main(){int m=0;char ch;while( (ch=getchar() )!='\n')if((ch>='a'&&ch<='z')||(ch>='A'&&ch<='Z'))m++;printf("%d\n",m);}}第5章后练习把100～200之间的不能被3整除的数输出。

main( ){ int n;for(n=100; n<=200; n++){ if(n%3 ==0)continue; printf(“%5d” , n);}}例: 问程序输出的结果?main(){ int i=1,a=0;for(; i<=5; i++){do {i++;a++;} while(i<3);i++; }printf(“a=%d,i=%d\n”,a,i);}输出:a=3 ,i=8例: 找出所有的三位数,它和它的各位数字的立方和正好相等. 例如:153=13+53+33.设所求的三位数,其百位数字是i,十位数字是j,个位数字是k. 显然应满足如下表达式:i*i*i+j*j*j +k*k*k = 100*i+10*j+kmain( ){ int i,j,k;for(i=1; i<=9; i++)for(j=0; j<=9; j++)for(k=0; k<=9; k++)if(i*i*i+j*j*j +k*k*k = =100*i+10*j+k )printf(“%d%d%d\n”, i,j, k);}第6章后练习示例: 输入2个数，如果它们的值不相等，则交换并输出它们的值；否则，输出“equal”。

交换a和b值的方法:temp=a;a=b;b=temp;#include <stdio.h>void main( ){ int a, b, temp;printf("input a, b: ");scanf("%d%d", &a, &b);if(a != b){temp = a;a = b;b = temp;printf("a = %d, b = %d\n", a, b); }elseprintf("equal\n");}示例: 输入3个整数，输出其中的最大值#include <stdio.h>void main( ){int a, b, c, max;printf("input a, b, c: ");scanf("%d%d%d", &a, &b, &c);max = a;if(max < b) max = b;if(max < c) max = c;printf("max is %d\n", max);}例: 输入x,计算下列分段函数f(x).1/x x≠0f(x)=0 x=0#include <stdio.h>void main(){float x,y;printf("input x: \n");scanf("%f",&x);if ( x != 0 ) y = 1/x;else y = 0;printf("f(%f) = %.2f\n", x, y);}例: 输入x,计算下列分段函数f(x).x+1 x <1f(x)= x+2 1≤x<2x+3 x ≥2#include<stdio.h>void main( ){ double x,y;printf("请输入x：");scanf("%lf",&x);if(x<1)y=x+1;else if(x<2)y=x+2;elsey=x+3;printf("f(%.2f)=%.2f\n",x,y);}7. 将大写字符转换为小写.#include<stdio.h>void main(){ char ch;while((ch=getchar())!='\n'){ if(ch>='A'&&ch<='Z'){ch+=32;printf("%c",ch);}elseprintf("%c",ch); }printf("\n");}8. 统计字符#include <stdio.h>#include <math.h>int main(){ char ch;int x=0,y=0,z=0,a=0,b=0;printf("请输入:\n");while((ch=getchar())!='\n'){ if(ch>='a'&&ch<='z')x++;else if(ch>='A'&&ch<='Z')y++;else if(ch>='0'&&ch<='9')z++;else if(ch==' '||ch=='\n')a++;elseb++;}printf("小写字母%d个\n",x);printf("大写字母%d个\n",y);printf("数字字符%d个\n",z);printf("空格字符%d个\n",a);printf("其它字符%d个\n",b);return 0;}9．计算分段函数#include<stdio.h>void main(){ float x,y;printf("请输入x:\n");scanf("%f",&x);if(x<=1)y=x+5;else if( x>1&&x<=10 )y=2*x;elsey=(3/(x-10);printf("x=%f y=%f\n",x,y);}10.五分制与百分制的转换#include<stdio.h>void main(){ int x,i;printf("该程序功能为五分制与百分制的转换!\n");printf("1 进入, 2 退出!\n");scanf("%d",&i);while(i==1){ printf("请输入:\n");scanf("%d",&x);if(x>=90 && x<=100)x=5;else if(x>=80 && x<90)x=4;else if(x>=70&&x<80)x=3;else if(x>=60&&x<70)x=2;elsex=1;printf("五分制成绩为%d分\n",x);printf(“1 继续2 退出!\n");scanf("%d",&i);}}第7章后练习1．百分制转换成五分制.#include<stdio.h>int main(){int x;printf("请输入学生百分制成绩:\n输入负数结束程序:\n");scanf("%d",&x);while(x>0){ switch(x/10){case 10: case 9:printf("五分制为:\n5\n\n");break; case 8:printf("五分制为:\n4\n\n");break;case 7:printf("五分制为:\n3\n\n");break;case 6:printf("五分制为:\n2\n\n");break;default:printf("五分制为:\n1\n\n");break;}printf("请输入学生百分制成绩:\n输入负数结束程序:\n");scanf("%d",&x);}printf("谢谢使用，再见:\n");return 0;}2．计算sin(),cos(),tan().#include <stdio.h>#include<math.h>int main(){double x,s;int y;printf("Input a number:\n");scanf("%lf",&x);while(1){printf("您希望进行哪种运算?\n");printf("1.计算sin(x)\n");printf("2.计算cos(x)\n");printf("3.计算tan(x)\n");scanf("%d",&y);switch(y){ case 1: s=sin(x);printf("sin(%f)=%f\n",x,s);break;case 2: s=cos(x);printf("cos(%f)=%f\n",x,s);break;case 3: s=tan(x);printf("tan(%f)=%f\n",x,s);break;default:printf(“输入有误，请输入1 - 3之间的数字！\n");}If(y==1||y==2||y==3)break;}printf("谢谢使用:\n");return 0;}。