有人可以解释一下如何获得此功能的输出？

Question

int main(int i, int j) {  
for (i=4; i>0; i--) {  
    j=i;    
    while (j>=0) {  
        printf("X");  
        j--;  
        }  
    printf("%lf\n", (1.0*(i)) / (j+2));  
    }  
}

Output:

XXXXX 4.0  
XXXX 3.0  
XXX 2.0  
XX 1.0  

Answer 1

The >= sign is probably confusing you. The code prints out X 5 times in the first row instead of 4 (if that's what you mean) is because once j = 0 , the loop continues once more.

Basically, the value of j after the while loop ends is -1 . Substitute it into your last printf and the rest of the output makes sense.

If you change the >= to a > , the code will produce the correct output.

Answer 2

why does the first line print 5 "X's"? & why is the first number 4.0?

Because,

j takes values of j = 4,3,2,1,0. Each time it is printing X hence 5X.

After that loop j becomes -1.

Now 1.0*(4) /(-1+2) => (4.0/1) => 4.0

Hence the output is XXXXX 4.0

Answer 3

Well, j is set to i , so it prints X j+1 times due to the >= 0 check. Then divides i by j , now -1 + 2. which is now one, to get i , which it prints to the screen before a newline begins.