剑指offer - 面试题52：构建乘积数组

package Chapter8;
/*
 * ans[i] = arr!/arr[i] (不能用除法)
 */
public class _52_array_construction {
  public static void main(String[] args) {
    int []arr = {1, 2, 3, 4, 5};
    new _52_function().array_construction(arr);
  }
}
class _52_function {
  void array_construction(int []arr_1) {
    int len = arr_1.length;
    int []arr_2 = new int[len];
    int []arr_3 = new int[len];
    arr_2[0] = arr_3[len - 1] = 1;
    for (int i = 1; i < len; i++) {
      arr_2[i] = arr_1[i - 1] * (i == 1 ? 1 : arr_2[i - 1]);
      arr_3[len - 1 - i] = arr_1[len - i] * (i == 1 ? 1 : arr_3[len - i]);
    }
    int []ans = new int[len];
    for (int i = 0; i < len; i++) {
      ans[i] = arr_2[i] * arr_3[i];
      System.out.print(ans[i] + "/ ");
    }
  }
}