简单背包问题

package main

import (
	"fmt"
	"sort"
)

type Item struct {
	Weight int
	Value int
	Ratio float64
}

func NewItem(weight int, value int) Item {
	item := Item {
		Weight: weight,
		Value: value,
	}
	item.Ratio = float64(value) / float64(weight)
	return item
}

type Items []Item

func (is Items) Len() int {
	return len(is)
}
func (is Items) Less(i, j int) bool {
	return is[i].Ratio <= is[j].Ratio
}
func (is Items) Swap(i, j int) {
	is[i], is[j] = is[j], is[i]
}
func main()  {
	capacity := 10
	highestValue := 0.0
	weights := []int{4, 6, 3, 2, 5}
	values := []int{9, 3, 1, 6 ,5}
	items := make(Items, 0, len(weights))
	for i :=0 ; i < len(weights); i ++ {
		item := NewItem(weights[i], values[i])
		items = append(items, item)
	}
	sort.Sort(sort.Reverse(items))
	for _, item := range items {
		if item.Weight <= capacity {
			capacity -= item.Weight
			highestValue += float64(item.Value)
		} else {
			highestValue += float64(capacity) / float64(item.Weight) * float64(item.Value)
			break
		}
	}
	fmt.Println(highestValue) // 19
}