下面 count_triple 函数的时间复杂度为(     )。

int count_triple(int n) {

int cnt = 0;

for (int a = 1; a <= n; a++)

for (int b = a; a + b <= n; b++)

for (int c = b; a + b + c <= n; c++)

if (a * a + b * b == c * c)

cnt++;

return cnt;

}