明解C语言（入门篇）第四章

练习4-2

#include<stdio.h>

int main(void)
{
   
      
    int a,b,n,m;
    int sum = 0;
    printf("请输入两个整数:\n");
    printf("整数a：");scanf("%d",&a);
	printf("整数b：");scanf("%d",&b);
	if (a > b){
   
   
		n = b;
		do{
   
   
			sum = n+sum; 
			n++;
		}while(n<=a);
		printf("大于等于%d小于等于%d的所有整数的和是%d。",b,a,sum);
	}		
	else{
   
   
		n = a;
		do{
   
   
			sum = n+sum;
			n++; 
		}while(n<=b);
		printf("大于等于%d小于等于%d的所有整数的和是%d。",a,b,sum);	
	}			
    return 0;
}

练习4-6

#include<stdio.h>

int main(void)
{
   
      
	int no;
	
	printf("请输入一个整数：");
	scanf("%d",&no);
	
	int i = 2;
	while(i<no){
   
   
		if(i%2==0){
   
   
			printf("%d ",i);
		}
		
		i+=2;
	}
	
    return 0;
}

练习4-7

#include<stdio.h>

int main(void)
{
   
      
	int no;
	
	printf("请输入一个正整数：");
	scanf("%d",&no);
	
	int i = 2;
	while(i<no){
   
   
		printf("%d ",i);
		i *=2;
	}
	
    return 0;
}

练习4-9

#include<stdio.h>

int main(void)
{
   
      
	int no;
	
	printf("正整数：");
	scanf("%d",&no);
	
	int i = 1;
	while(i<=no){
   
   
		if(i%2==0){
   
   
			printf("-");
		}
		else{
   
   
			printf("+");
		}
		i+=1;