golang中的if else语句

Question

Could someone help me debug this program, only the else part is processed on every input. This id a program for grading students. a student inputs a mark and the the grade is displayed

func main(){
    var x int
    fmt.Println("Enter your marks")

    fmt.Scanf("%d",&x)

    if (100 <= x) && (x<=75){
        fmt.Println("D1")
    }else if (74 <= x)&&(x <= 70){
        fmt.Println("D2")
    }else if (69 <= x )&&(x<=65){
        fmt.Println("C3")
    }else if (64 <= x)&&(x <= 60){
        fmt.Println("C4")
    }else if (59 <= x)&&(x <= 55){
        fmt.Println("C5")
    }else if (54 <= x)&&( x<= 50){
        fmt.Println("C6")
    }else if (49 <= x )&&(x<= 45){
        fmt.Println("P7")
    }else{
        fmt.Println("Work harder")
    }
}

Answer 1

You have a logic problem.

Change

if (100 <= x) && (x<=75){

to

if 75 <= x && x <= 100 { // numbers here are ordered from smallest to greatest

because a number can't be greater than 100 and smaller than 75.

And it's the same for the other lines of course.

Note that you could make less comparisons. Suppose you test if the number is smaller than 100 initially, then you don't have to test if it's smaller than 75 just after you tested it's smaller than 75.

A typical Go code would probably have a switch here instead of all those if/else. See switch in the documentation. Here's how it could be written with a switch :

switch {
case x > 100:
    fmt.Println("Congrats!") // you forgot this one
case x >= 75:
    fmt.Println("D1")
case x >= 70:
    fmt.Println("D2")
case x >= 65:
    fmt.Println("C3")
case x >= 60:
    fmt.Println("C4")
case x >= 55:
    fmt.Println("C5")
case x >= 50:
    fmt.Println("C6")
case x >= 45:
    fmt.Println("P7")
default:
    fmt.Println("Work harder")
}

A last comment : This type of switching code rarely occurs because normally the thresholds and related notes are stored as data, for example in a struct.