剑指Offer 52 构建乘积数组

题目描述

给定一个数组A[0,1,…,n-1],请构建一个数组B[0,1,…,n-1],其中B中的元素B[i]=A[0]A[1]…A[i-1]A[i+1]…A[n-1]。不能使用除法。

思路

1. 想想一个矩阵

   代码

   public int[] multiply(int[] A) {
          int length = A.length;
          int [] C = new int[length];
          int [] D = new int[length];
          int [] B = new int[length];
          C[0] = 1;
          D[0] = 1;
          for (int i = 1; i < length; i++) {
              C[i] = A[i-1] * C[i-1];
              D[i] = A[length-i] *D[i-1];
          }
          for (int i = 0; i < length; i++) {
              B[i] = C[i] * D[length-i-1];
          }
          return  B;
      }