如何为数组的最后一个元素添加特殊条件

Question

根据任务描述，输出应该是一个新数组，其中数组 days 的所有元素都大于其上一个和下一个元素（以 1 为增量）。例如，我们有作为输入

[ ]int{3, 2, 4, 3, 7, 9}

输出应该是：

[ ]int{3, 4, 9}

起初我试着写下一个条件：

if days[i] > days[i-1] && days[i] > days[i+1] {

            arr = append(arr, days[i])

        }

但发生错误：index out of range [-1]

然后我改变了条件并为最后一个元素添加了一个特殊条件：

package main

import (

    "fmt"

)

func chaos(days []int) []int {

    var arr []int

    for i := 0; i < len(days)-1; i++ {

        if days[i] > days[i+1] {

            arr = append(arr, days[i])

        }

        if days[len(days)-1] > days[len(days)-2] {

            arr = append(arr, days[len(days)-1])

        }

    }

    return arr

}

func main() {

    fmt.Println(chaos([]int{3, 2, 4, 3, 7, 9}))

}

但输出是[3 9 9 4 9 9 9]

如何正确指定最后一个元素的条件以及为什么我的结果不正确？

Answer 1

9多次填充的原因是因为您在循环if内使用以下条件for。将其放在循环if之外for，然后您将获得所需的输出：if days[len(days)-1] > days[len(days)-2] {&nbsp; &nbsp; &nbsp; &nbsp; arr = append(arr, days[len(days)-1])&nbsp; &nbsp; }但是，除此之外，您还只是将i'th元素与下一个元素进行比较。根据问题，您还应该将它与之前的元素进行比较。以下是可以在您的代码中进行的可能更改以正常工作：package mainimport (&nbsp; &nbsp; "fmt")func chaos(days []int) []int {&nbsp; &nbsp; var arr []int&nbsp; &nbsp; fmt.Println(len(days))&nbsp; &nbsp; if days[0] > days[1] {&nbsp; &nbsp; &nbsp; &nbsp; arr = append(arr, days[0])&nbsp; &nbsp; }&nbsp; &nbsp; for i := 1; i < len(days)-1; i++ {&nbsp; &nbsp; &nbsp; &nbsp; if (days[i] > days[i+1]) && (days[i] > days[i-1]) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; arr = append(arr, days[i])&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; }&nbsp; &nbsp; if days[len(days)-1] > days[len(days)-2] {&nbsp; &nbsp; &nbsp; &nbsp; arr = append(arr, days[len(days)-1])&nbsp; &nbsp; }&nbsp; &nbsp; return arr}func main() {&nbsp; &nbsp; fmt.Println(chaos([]int{3, 2, 4, 3, 7, 9}))}https://go.dev/play/p/ndJVc35TM1O

Answer 2

您可以将math.MinInt64（可以视为负无穷大）添加到切片的开始和结束，以轻松处理两种边缘情况。然后从一个索引开始迭代1到另一个索引n-2（通过排除0和n-1我们添加的条目）。我会像下面那样尝试。package mainimport (&nbsp; &nbsp; "fmt"&nbsp; &nbsp; "math")func chaos(days []int) []int {&nbsp; &nbsp; var arr []int&nbsp; &nbsp; // Add negative infinity to the start&nbsp; &nbsp; days = append([]int{math.MinInt64}, days...)&nbsp; &nbsp; // Add negative infinity to the end&nbsp; &nbsp; days = append(days, math.MinInt64)&nbsp; &nbsp; for i := 1; i <= len(days)-2; i++ {&nbsp; &nbsp; &nbsp; &nbsp; if (days[i] > days[i+1]) && (days[i] > days[i-1]) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; arr = append(arr, days[i])&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; }&nbsp; &nbsp; return arr}func main() {&nbsp; &nbsp; fmt.Println(chaos([]int{3, 2, 4, 3, 7, 9}))}