238. Product of Array Except Self
Given an array nums of n integers where n > 1, return an array output such that output[i] is equal to the product of all the elements of numsexcept nums[i].
Example:
Input: [1,2,3,4] Output: [24,12,8,6]
Note: Please solve it without division and in O(n).
Follow up: Could you solve it with constant space complexity? (The output array does not count as extra space for the purpose of space complexity analysis.)
思路：
当前位置的左边全部相乘，右边全部相乘，然后全乘起来就可以。乘右边的时候可以倒着计算就可以两边循环就得出结果。
代码：
java：
代码语言：javascript复制class Solution {
public int[] productExceptSelf(int[] nums) {
int len = nums.length;
int[] res = new int[len];
res[0] = 1;
// left multi
for (int i = 1; i < len; i ) {
res[i] = res[i-1] * nums[i-1];
}
// right multi
int right = 1;
for (int i = len -1; i >= 0; i--) {
res[i] *= right;
right *= nums[i];
}
return res;
}
}
