while(i<=100)
??? {
??????
??????? //sum=sum+flag*i;
??????? //flag=-flag;
??????? i++;
??? }
???
??? i = 1;? //重新初始化變量i
???
??? //do-while循環(huán)
??? do{
???????
??????? //sum=sum+flag*i;
??????? //flag=-flag;
??????? i++;
??? }while(i<=100);
???
??? i = 1;? //重新初始化變量i
???
??? //使用for循環(huán)
??? for(i=1;i<=100;i++)
??? {
??????? sum=sum+flag*i;
??????? flag=-flag;
??????? i++;
??? }?
??? printf("sum=%d\n",sum);
???
??? return 0;???
}

當DO?while for?連用時，為什么前兩個條件前加//