下面 count_triple 函数的时间复杂度为( )。
1 int count_triple(int n) { 2 int cnt = 0; 3 for (int a = 1; a <= n; a++) 4 for (int b = a; a + b <= n; b++) { 5 int c = sqrt(a * a + b * b); 6 if (a + b + c > n) 7 break; 8 if (a * a + b * b == c * c) 9 cnt++; 10 } 11 return cnt; 12 }
O(n)
O(n2)
O(n3)
O(n4)