第3章_源程序代码

第3章选择结构程序设计P75【例3-5】的源程序# include <stdio.h>main( ){ int x , y ;printf("Please input a number (int): ") ;scanf("%d" ,&x ) ;y = x ;if ( y < 0 ) y = -y ;printf(" \n x = %d y = %d \n" ,x , y ) ;}P75【例3-6】的源程序程序1：# include <stdio.h>main(){ int a , b , max ;printf(" Input two numbers :" ) ; /* 输出提示信息*/scanf("%d , %d" , &a , &b ) ; /* 输入a ,b的值*/if( a > b ) max = a ;else max = b ;printf("The max number is%d \n" ,max ) ;}P76程序2：# include <stdio.h>main(){ int a , b , max ;printf(" Input two numbers :" ) ;scanf("%d , %d" , &a , &b ) ;max = a ;if( max < b ) max = b ;printf("The max number is%d \n" ,max ) ;}P76【例3-7】# include <stdio.h>main( ){ int a , b , c , max , min ;printf("请输入整数a , b , c：") ;scanf("%d ,%d ,%d" ,&a , &b , &c ) ;if( a > b ) { max = a ; min = b ; }else { max = b ; min = a ; }if( c > max ) printf(" %d , %d , %d \n" ,c , max , min ) ;else if( c < min ) printf(" %d , %d , %d \n" ,max , min , c) ;else printf(" %d , %d , %d \n" ,max , c , min ) ;}P77【例3-8】# include <stdio.h># include <math.h>main(){ int x ;float y ;scanf("%d" , &x ) ;if( x < 0 ) y =( float ) x ;else { if ( x < 10 ) y = ( float ) (3*x*x –1 ) ; /* x >= 0且x < 10时*/else y = ( float ) sqrt ( 3*x + 1 ) ; /* x >= 10时*/}printf(" x = %d , y = %.2f \n " ,x , y ) ;}三、任务的实现1）一科成绩的合法性判定（2）实现的程序P78# include <stdio.h>main(){ int sc ;printf(" \n请输入学生成绩: " ) ;scanf("%d" ,&sc ) ;if ( sc >= 0 && sc<= 100 ) printf("成绩输入正确！") ;else printf("成绩输入错误! " ) ;}P792）一科成绩的及格与否评定（2）实现的程序实现的程序# include <stdio.h>main( ){ int sc ;printf(" \n 请输入学生成绩: ") ;scanf("%d" , &sc ) ;if( sc >= 60 ) printf("及格!") ;else printf("不及格!") ;}P793）多科成绩的合法性判定及通过与否评定（2）实现的程序实现的程序# include <stdio.h>main( ){ int sc_A , sc_B ; /* sc_A和sc_B用于存放两科成绩*/ printf("请输入两科成绩以空格分隔:" ) ;scanf("%d%d" , &sc_A , &sc_B ) ;if( sc_A >= 60 ) /* 判断A科成绩*/if( sc_B >= 60 ) printf ("两科通过获取资格证书！\n" ) ;else printf ("A科通过！\n" ) ;elseif( sc_B >= 60 ) printf ("B科通过！\n" ) ; /* 判断B科成绩*/else printf ("两科均未通过！\n" ) ;}P80【例3-9】# include <stdio.h>main( ){ nt a = 0 , b = 2 , c = 1 , d = 3 ;c = a && ( ++b ) ;d = b || ( ++ a ) ;printf("%d , %d , %d , %d \n " ,a , b , c , d ) ;}P81【例3-10】# include <stdio.h>main(){ int a , b , max ;scanf("%d , %d" , &a , &b ) ;max = ( a > b ) ? a : b ;printf("The max number is%d \n" ,max ) ;}P81【例3-11】# include <stdio.h>main( ){ char ch ;scanf("%c" ,&ch ) ; /* 大小写字母的ASCII码值差32*/ch = ( ch >= 'A'&&ch <= 'Z' ) ? ( ch + 32 ) : ch ;printf(" %c \n " ,ch ) ;}P82【例3-12】# include <stdio.h>main( ){ int x , y ;scanf("%d" ,&x ) ;y = ( x < 0 ) ? ( -1* x ) : ( ( x > 0 ) ? x : 0 ) ;printf(" x = %d , y = %d \n " ,x , y ) ;}P82【例3-13】# include <stdio.h>main( ){ float h , x , y ;printf("请输入全票价格(元): " ) ;scanf("%f" ,&x ) ;printf("请输入儿童身高(米): " ) ;scanf("%f" ,&h ) ;if ( h < 1.1) y = 0.0f ; /* 通过对儿童身高的判断计算票价*/else if( h < 1.5) y = x /2.0f ;else y = x ;printf("儿童应购票价格为: %.2f 元\n " , y ) ;}P85【例3-14】# include <stdio.h>main(){ int a , b ;char ch ;scanf("%c" , &ch ) ;srand( ( unsigned ) time ( NULL ) ) ; /* 也可用srand( time ( NULL ) ) ; */a = rand( ) %10 ;b = rand( ) %10 ;switch( ch ){ case '+' : printf(" %d + %d = " , a , b ) ; break ;case '-' : printf(" %d - %d = " , a , b ) ; break ;case '*' : printf(" %d * %d = " , a , b ) ; break ;case '/' : printf(" %d / %d = " , a , b ) ; break ;default : printf(" 输入有错！\n " ) ;}}P85【例3-15】# include <stdio.h>main(){ int a , b , c ; a = 1 ; b = 2 ; c = 3 ;switch( a ){ case 0 : switch( b ){ case 1 : printf( " ! " ) ; break ;case 2 : printf( " @ " ) ;} break ; /* 注意此处的break语句！*/case 1: switch( c ==3 ){ case 0 : printf(" # " ) ; break ;case 1 : printf(" $ " ) ; break ;default : printf(" * " ) ;}}}P85【例3-16】# include <stdio.h>main( ){ long profit ; /* profit存放销售额*/double d1 , d2 , d3 , d4 ; /* d1~d4存放提成比例*/int grade ; /* grade存放销售额整除1000后的值*/double gz1 , gz2 , gz3 ; /* gz1、gz2、gz3分别存放基本工资、提成工资、月工资*/ gz1 = 800 ;printf( "请输入销售额: ") ; scanf("%ld" , &profit ) ;if ( profit >= 5000 ) grade = 5 ;else grade = profit / 1000 ; /* 将销售额整除1000，转化成case子句中的常量*/switch( grade ){ case 0 : d1 = 0.0 ; gz2 = 0 ; break ;case 1 :d2 = 0.10 ; gz2 = ( profit -1000 ) * d2 ; break ;case 2 :case 3 :case 4 : d3 = 0.15 ; gz2 = (profit -2000 )*d3+ 1000*d2 ; break ;case 5 :d4 = 0.20 ; gz2 = (profit -5000 )*d4 +3000*d3 + 1000*d2 ;break ;default : grade = -1 ;}if ( grade ==-1 ) printf(" The profit input error! \n " ) ;else { gz3 = gz1 + gz2 ; /* 月工资= 基本工资+提成工资*/printf("本月工资为：%.2f \n " ,gz3 ) ;}}三、任务的实现P87等级成绩转化为数值成绩（2）实现的程序：实现的程序：# include <stdio.h>main(){ char grade ; int cj ;printf(" Input a grade ( A ~ E ) : " ) ;scanf("%c" ,&grade ) ;switch( grade ){ case 'A' : cj = 95 ;break ;case 'B' : cj = 85 ; break ;case 'C' : cj = 75 ; break ;case 'D' : cj = 65 ; break ;case 'E' : cj = 45 ; break ;default : cj = -1 ;}if ( cj ==-1 ) printf(" 输入有错！\n " ) ;else printf(" %c - %d \n " , grade , cj ) ;}。