GCJ/2008/1A/A/main.go

package main

import (
	"bufio"
	"fmt"
	"os"
	"sort"
)

func minProduct(scanner *bufio.Scanner) []int64 {
	caseCnt := ReadInt(scanner) // Math AGAIN.
	answer := make([]int64, caseCnt)
	for i := 0; i < caseCnt; i++ {
		// n = 2 is a very impotant case, because:
		// if x < x', y < y', then xy'+x'y - xy - x'y'
		// = -(x' - x)(y' - y) < 0, so xy'+x'y < xy + x'y'
		vecDim := ReadInt(scanner)
		vec1 := ReadInts(scanner)
		vec2 := ReadInts(scanner)
		sort.Ints(vec1)
		sort.Ints(vec2)
		for j := 0; j < vecDim; j++ {
			answer[i] += int64(vec1[j] * vec2[vecDim-1-j])
		}
	}
	return answer
}

func main() {
	inputFiles := []string{"A-small-practice.in", "A-large-practice.in", "test.in"}
	outputFiles := []string{"result-small.out", "result-large.out", "test.out"}
	const (
		small = iota
		large
		test
	)

	fileType := large

	fin, _ := os.Open(inputFiles[fileType])
	defer fin.Close()

	scanner := bufio.NewScanner(fin)
	answer := minProduct(scanner)

	fout, _ := os.Create(outputFiles[fileType])
	defer fout.Close()

	for i, n := range answer {
		s := fmt.Sprintf("Case #%d: %d\n", i+1, n)
		fout.WriteString(s)
	}
}