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

代码

import Strategy.Strategy;import java.lang.reflect.Array;import java.util.Arrays;public class MultiArr {    public static void main(String[] args){        MultiArr multiArr = new MultiArr();        int[] a = {1, 2, 3,4,5};//        int[] a = {1,2};        /*int[] a = {1, 2, 3,4,5,6};        int[] a = {1, 2, 3,4,5,6};*/        int[] multiply = multiArr.multiply(a);        System.out.println(Arrays.toString(multiply));    }    public int[] multiply(int[] A) {        //注意特殊case        if(A.length == 0 || A == null)return A;        if(A.length == 1) return A;        int len = A.length;        int[] B = new int[len];        int[] C = new int[len];        //设置数组C和D的初始值        C[0] = 1;        C[1] = A[0];        int[] D = new int[len];        D[len - 1] = 1;        D[len - 2] = A[len - 1];        //需要注意的就是两个for循环的边界条件        for(int i = 1; i < len - 1; i++){            C[i + 1] = C[i ] * A[i];        }        for(int i = len - 2; i >= 0; i--){            D[i] = D[i+1] * A[i+1];        }        for(int i = 0; i < len; i++){            B[i] = C[i] * D[i];        }        return B;    }}