Google Code Jam 2015 * Round 1A * Problem A. Mushroom Monster

A.go

/*
 *  Google Code Jam
 *  2015 Round 1A
 *  Problem A. Mushroom Monster
 *  AQ <aq@okaq.com>
 */
package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"strings"
	"sync"
	"time"
)

const (
	IN  = "A-large-practice.in"
	OUT = "A-large-practice.out"
)

var (
	I  *os.File
	O  *os.File
	S  *bufio.Scanner
	W  *bufio.Writer
	T  int
	Sh []*Shroom
	WG sync.WaitGroup
)

type Shroom struct {
	N int
	M []int
	Y int
	Z int
}

func NewShroom() *Shroom {
	return &Shroom{}
}

func (sh *Shroom) Solve() {
	sh.Y = sh.First()
	sh.Z = sh.Second()
	WG.Done()
}

func (sh *Shroom) First() int {
	min := 0
	for i := 1; i < sh.N; i++ {
		min += Max(0, sh.M[i-1]-sh.M[i])
	}
	return min
}

func (sh *Shroom) Second() int {
	max := 0
	for i := 1; i < sh.N; i++ {
		max = Max(max, sh.M[i-1]-sh.M[i])
	}

	min := 0
	for i := 0; i < sh.N-1; i++ {
		min += Min(sh.M[i], max)
	}
	return min
}

func Max(a, b int) int {
	if a > b {
		return a
	}
	return b
}

func Min(a, b int) int {
	if a < b {
		return a
	}
	return b
}

func Load() {
	var err error
	I, err = os.Open(IN)
	if err != nil {
		fmt.Println(err)
	}
	S = bufio.NewScanner(I)
	O, err = os.Create(OUT)
	if err != nil {
		fmt.Println(err)
	}
	W = bufio.NewWriter(O)
}

func Cases() {
	var err error
	S.Scan()
	T, err = strconv.Atoi(S.Text())
	if err != nil {
		fmt.Println(err)
	}
	fmt.Printf("%d test cases. \n", T)
}

func Split() {
	var err error
	Sh = make([]*Shroom, T)
	for i := 0; i < T; i++ {
		sh := NewShroom()
		S.Scan()
		sh.N, err = strconv.Atoi(S.Text())
		S.Scan()
		a := strings.Split(S.Text(), " ")
		sh.M = make([]int, len(a))
		for j := 0; j < len(a); j++ {
			sh.M[j], err = strconv.Atoi(a[j])
		}
		if err != nil {
			fmt.Println(err)
		}
		Sh[i] = sh
		// fmt.Println(sh)
		WG.Add(1)
		go Sh[i].Solve()
	}
}

func Finish() {
	defer I.Close()
	defer O.Close()
	for i := 0; i < T; i++ {
		s0 := fmt.Sprintf("Case #%d: %d %d\n", i+1, Sh[i].Y, Sh[i].Z)
		W.WriteString(s0)
	}
	W.Flush()
}

func main() {
	begin := time.Now()
	fmt.Println("mushroom monster ok!")
	Load()
	Cases()
	Split()
	WG.Wait()
	Finish()
	end := time.Now()
	fmt.Printf("total run time: %v.\n", end.Sub(begin))
}

// fast linear accumulation solutions
// total run time: 111ms large input