58 lines
1.3 KiB
Go
58 lines
1.3 KiB
Go
package top100liked
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import (
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"fmt"
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"testing"
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)
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// https://leetcode.cn/problems/product-of-array-except-self/?envType=study-plan-v2&envId=top-100-liked
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// func productExceptSelf(nums []int) []int {
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// left := make([]int, len(nums))
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// right := make([]int, len(nums))
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// left[0] = nums[0]
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// right[len(nums)-1] = nums[len(nums)-1]
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// for i := 1; i < len(nums); i++ {
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// left[i] = left[i-1] * nums[i]
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// }
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// for i := len(nums) - 2; i >= 0; i-- {
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// right[i] = right[i+1] * nums[i]
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// }
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// res := []int{}
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// for i := range nums {
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// if i == 0 {
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// res = append(res, right[1])
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// } else if i == len(nums)-1 {
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// res = append(res, left[len(nums)-2])
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// } else {
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// res = append(res, left[i-1]*right[i+1])
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// }
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// }
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// return res
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// }
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func productExceptSelf(nums []int) []int {
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n := len(nums)
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answer := make([]int, n)
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// 第一遍：计算左边乘积，存入 answer
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answer[0] = 1
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for i := 1; i < n; i++ {
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answer[i] = answer[i-1] * nums[i-1]
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}
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// 第二遍：从右向左，用 R 维护右边乘积
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R := 1
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for i := n - 1; i >= 0; i-- {
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answer[i] = answer[i] * R // 左边积 × 右边积
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R = R * nums[i] // 更新右边积
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}
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return answer
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}
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func TestS16(t *testing.T) {
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fmt.Printf("%+v", productExceptSelf([]int{1, 2, 3, 4}))
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fmt.Printf("%+v", productExceptSelf([]int{-1, 1, 0, -3, 3}))
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}
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