将while循环转换为for循环会导致无限循环

Question

I've been having converting a while loop to a for loop. The problem I am having is the while loop works as intended, but when compiled the for loop causes an infinite loop. Any help would be awesome!

int y1 = 1776;
int y2 = 2008;

while(y1 <= y2){
    ++ y1;
    if( (y1%400==0 || y1%100!=0) &&(y1%4==0))
        cout << y1 <<" "<< "Is a Leap Year" << " ";
}
cout <<"Now with a for loop" << endl;

for(y1 <= y2; ++ y1;)
{
    if( (y1%400==0 || y1%100!=0) &&(y1%4==0))
        cout << y1;
}

Answer 1

you are very close but:

for(y1 <= y2; ++ y1;)
                   ^

should be:

for(;y1 <= y2; ++ y1)
    ^

note that because you are skipping any initializing, ie the usual int i = 0 then you should make sure that its the first placer that is empty, not the last since for loops are structured like:

for(initialize stuff here; boolean here; iterator here)

Answer 2

int y1 = 1776;
int y2 = 2008;

for(;y1 <= y2; ++y1)
{
    if( (y1%400==0 || y1%100!=0) &&(y1%4==0))
        cout << y1;

}

Since y1 has already a value, you can leave the initialization of the for loop empty.

Answer 3

Your loop isn't complete. It should look like:

for (int y1 = 0; y1 <= y2; y1++)

Answer 4

Please take the time to do a fast google search to see the right syntax for a for loop. Here it is : http://www.cplusplus.com/doc/tutorial/control/