【基础入门题】Golang 004. 转换百分制分数

给出一个百分制成绩，要求输出等级为A,B,C,D,E。
90分以上即n>=90为A；80<=n<90分为B；以此类推；
直到n<60分全为E；如果输入小于0或大于100的分数，
则输出“Not valid”。

输入形式：输入一个可能带小数点的分数
输出形式：根据对应关系，输出五分制分数档。 

方法一： if - else if - else 

package main

import "fmt"

func Grade(m float32) string {
	var result string
	if m <= 100 && m >= 90 {
		result = "A"
	} else if m < 90 && m >= 80 {
		result = "B"
	} else if m < 80 && m >= 70 {
		result = "C"
	} else if m < 70 && m >= 60 {
		result = "D"
	} else if m < 60 && m >= 0 {
		result = "E"
	} else {
		result = "Not valid"
	}
	return result
}

func main() {

	fmt.Printf("Grade(%.1f) = %s\n", 80.5, Grade(80.5))
	fmt.Printf("Grade(%d) = %s\n", 100, Grade(100))
	fmt.Printf("Grade(%d) = %s\n", 105, Grade(105))

	/* Out:
	Grade(80.5) = B
	Grade(100) = A
	Grade(105) = Not valid
	*/

}

方法二： switch - case - default，switch后无表达式

package main

import "fmt"

func Grade(m float32) string {
	var result string
	switch {
	case m <= 100 && m >= 90:
		result = "A"
	case m < 90 && m >= 80:
		result = "B"
	case m < 80 && m >= 70:
		result = "C"
	case m < 70 && m >= 60:
		result = "D"
	case m < 60 && m >= 0:
		result = "E"
	default:
		result = "Not valid"
	}
	return result
}

func main() {

	fmt.Printf("Grade(%.1f) = %s\n", 80.5, Grade(80.5))
	fmt.Printf("Grade(%d) = %s\n", 100, Grade(100))
	fmt.Printf("Grade(%d) = %s\n", 105, Grade(105))

	/* Out:
	Grade(80.5) = B
	Grade(100) = A
	Grade(105) = Not valid
	*/

}

方法三： switch - case - default，switch后有表达式

package main

import "fmt"

func Grade(m float32) string {
	var result string
	if m > 100 || m < 0 {
		return "Not valid"
	}
	switch int(m) / 10 {
	case 10, 9:
		result = "A"
	case 8:
		result = "B"
	case 7:
		result = "C"
	case 6:
		result = "D"
	default:
		result = "E"
	}
	return result
}

func main() {

	fmt.Printf("Grade(%.1f) = %s\n", 80.5, Grade(80.5))
	fmt.Printf("Grade(%d) = %s\n", 100, Grade(100))
	fmt.Printf("Grade(%d) = %s\n", 105, Grade(105))

}

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