菜鸟 只a了两道比较简单的
第一题
思路：单调栈

package main
import "fmt"
func main() {
    var n, x int
    fmt.Scan(&n)
    var stack []int
    //stack := make([]int, n)
    //fmt.Scan(&x)
    for i := 0; i < n; i++ {
        fmt.Scan(&x)
        for len(stack) != 0 && x > stack[len(stack)-1] {
            stack = stack[:len(stack)-1]
        }
        stack = append(stack, x)
    }

    fmt.Println(len(stack))
    fmt.Print(stack[0])
    for j := 1; j < len(stack); j++ {
        fmt.Printf(" %d", stack[j])
    }
    fmt.Println(stack)
}

第二题：无思路
第三题：

package main

import (
    "bufio"
    "fmt"
    "os"
    "strings"
)

var m = map[string]string{}

func main() {
    var n int
    fmt.Scan(&n)
    input := bufio.NewReader(os.Stdin)
    for i := 0; i < n; i++ {
        line, _, _ := input.ReadLine()
        s := string(line)
        str := strings.Fields(s)
        //if str[0] == "Change" {
        //    Change(str[1], str[2], str[3])
        //} else if str[0] == "Add" {
        //    Adds(str[1], str[2], str[3])
        //} else if str[0] == "Delete" {
        //    Delete(str[1])
        //} else if str[0] == "Query" {
        //    Query(str[1])
        //}
        //优化成switch语句
        switch str[0] {
        case "Change":
            Change(str[1], str[2], str[3])
        case "Add":
            Adds(str[1], str[2], str[3])
        case "Delete":
            Delete(str[1])
        case "Query":
            Query(str[1])
        }
    }
}
func Change(s, x, y string) {
    if m[s] != "" {
        m[s] = x + " " + y
    }
}
func Delete(s string) {
    if m[s] != "" {
        delete(m, s)
    }
}
func Adds(s, x, y string) {
    m[s] = x + " " + y
}
func Query(s string) {
    if m[s] == "" {
        fmt.Println("no")
    } else {
        fmt.Println("yes")
        fmt.Println(m[s])
    }
}