数组应用，c语言，大一新手

请问大家，这个程序怎么理解呢，最后运行结果为什么就是21了？

就是这样呀！有用记得采纳呐

p[0] = a[0 * 1] = a[0] = 0;
p[1] = a[1 * 2] = a[2] = 2;
p[2] = a[2 * 3] = a[6] = 6
k = 5 + p[0] * 2 + p[1] * 2 + p[2] * 2 = 5 + 0 + 4 + 12 = 21

a很好理解，a = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
p[i] = a[i*(i+1)];，p = {0, 2, 6}
k += p[i] * 2;，k = 5 + 0×2 + 2×2 + 6×2 = 21