2021-08-23：超级水王问题。扩展1：摩尔投票。扩展2：给定一个正数K，返回所有出现次数＞N/K的数。

package main

import (
    "fmt"
)

func main() {
    arr := []int{1, 2, 1, 5, 1, 1, 2}
    printHalfMajor(arr)
    fmt.Println("--------")
    printKMajor(arr, 7)
}

func printHalfMajor(arr []int) {
    cand := 0
    HP := 0
    for i := 0; i < len(arr); i++ {
        if HP == 0 {
            cand = arr[i]
            HP = 1
        } else if arr[i] == cand {
            HP++
        } else {
            HP--
        }
    }
    if HP == 0 {
        fmt.Println("no such number.")
        return
    }
    HP = 0
    for i := 0; i < len(arr); i++ {
        if arr[i] == cand {
            HP++
        }
    }
    if HP > len(arr)/2 {
        fmt.Println(cand)
    } else {
        fmt.Println("no such number.")
    }
}

func printKMajor(arr []int, K int) {
    if K < 2 {
        fmt.Println("the value of K is invalid.")
        return
    }
    // 攒候选，cands，候选表，最多K-1条记录！> N / K次的数字，最多有K-1个
    cands := make(map[int]int)
    for i := 0; i != len(arr); i++ {
        if _, ok := cands[arr[i]]; ok {
            cands[arr[i]] = cands[arr[i]] + 1
        } else { // arr[i] 不是候选
            if len(cands) == K-1 { // 当前数肯定不要！，每一个候选付出1点血量，血量变成0的候选，要删掉！
                allCandsMinusOne(cands)
            } else {
                cands[arr[i]] = 1
            }
        }
    }
    // 所有可能的候选，都在cands表中！遍历一遍arr，每个候选收集真实次数

    reals := getReals(arr, cands)
    hasPrint := false
    for key, _ := range cands {
        if reals[key] > len(arr)/K {
            hasPrint = true
            fmt.Println(fmt.Sprintf("%d", key) + " ")
        }
    }
    if hasPrint {
        fmt.Println("")
    } else {
        fmt.Println("no such number.")
    }

}

func allCandsMinusOne(map0 map[int]int) {
    removeList := make([]int, 0)
    for key, value := range map0 {

        if value == 1 {
            removeList = append(removeList, key)
        }
        map0[key] = value - 1
    }
    for removeKey, _ := range removeList {
        delete(map0, removeKey)
    }
}

func getReals(arr []int, cands map[int]int) map[int]int {
    reals := make(map[int]int)
    for i := 0; i != len(arr); i++ {
        curNum := arr[i]
        if _, ok := cands[curNum]; ok {
            if _, ok2 := reals[curNum]; ok2 {
                reals[curNum] = reals[curNum] + 1
            } else {
                reals[curNum] = 1
            }
        }
    }
    return reals
}