*（a+k）就是取数组a的第k个元素，s = a[0] + a[2] + a[4] + a[6] = 5 + 7 + 1 + 3 = 16
int a[]={5,3,7,2,1,5,3,10},s=0,k; for(k=0;k<8;k+=2) s+=*(a+k);//s将a[0],a[2],a[4],a[6]相加和赋予s printf("%d",s);//s=16
