Question

No code is needed, only simple math theory.

Like:

• print “enter your age”
• read(age)
• if age>20
• result=”adult”
• print”you are”
• print(result)

I am going to attend C language classes but before that I want to learn some basics.
I need a program/algo that finds maximum and minimum of three numbers using multiple-if or nested-if.

Answer 1

There’s the straightforward way:

int min(int a, int b, int c){
    if (a <= b && a <= c){
        return a;
    }
    if (b <= a && b <= c){
        return b;
    }
    if (c <= a && c <= b){
        return c;
    }
}

There’s the way with the minimum number of comparisons:

int min(int a, int b, int c){
    if (a < b){
        if (a < c){
            return a;
        }
        else{
            return c;
        }
    }
    else{
        if (b < c){
            return b
        }
        else{
            return c;
        }
    }
}

There’s the way with the fewest lines of code, thanks to the ternary operator:

int min(int a, int b, int c){
    return (a<b)?((a<c)?a:c):((b<c)?b:c);
}

There’s the way twalberg mentioned in the comments:

int min(int a, int b){
    if (a <= b){return a;}
    else{return b;}
}

int min(int a, int b, int c){
    return min(min(a,b), c);
}

max can be defined in all of these ways too, replacing < with >. You can also define it in terms of min:

int max(int a, int b, int c){
    return -min(-a, -b, -c);
}

If you don’t wish to learn how to declare functions yet, you can drop some of these straight into your main function. For example, the second method:

//todo: translate this pseudocode into C
print "enter three numbers"
read(a)
read(b)
read(c)
if (a < b){
    if (a < c){
        min = a;
    }
    else{
        min = c;
    }
}
else{
    if (b < c){
        min = b
    }
    else{
        min = c;
    }
}
print "the minimum value is " + min