你漏了加“sum=0;”如代碼，希望采納！

#include?<stdio.h>
int?main()
{
????/*?小伙伴們：
???????????選擇你們認(rèn)為最合理的循環(huán)結(jié)構(gòu)完成功能吧?*/
????int?sum?=?0;??//定義計(jì)算結(jié)果變量sum
????int?i?=?1;????//定義循環(huán)數(shù)字變量i
????int?flag?=?1;?//定義符號(hào)狀態(tài)變量flag
????
????//使用while循環(huán)
????while(i<=100)
????{
????????i++;
????????sum+=i*flag;
????????flag*=-1;
????}
????sum=0;
????i?=?1;??//重新初始化變量i
????
????//do-while循環(huán)
????do{
????????i++;
????????sum+=i*flag;
????????flag*=-1;
????}while(i<=100);
????sum=0;
????i?=?1;??//重新初始化變量i
????
????//使用for循環(huán)
????for(i=1;i<=100;i++)
????{
????????sum+=i*flag;
????????flag*=-1;
????????
????}??
????printf("sum=%d\n",sum);?
????
????return?0;????
}

希望采納！希望采納！希望采納！希望采納！

一次只能用一個(gè)循環(huán)哦，你選擇用某種循環(huán)體的時(shí)候應(yīng)該把另外的兩個(gè)標(biāo)為注釋