Question

http://acm.hdu.edu.cn/showproblem.php?pid=2057

#include <stdio.h>

int main ( void )
{
__int64 a, b;
while ( scanf ( "%I64X %I64X", &a, &b ) != EOF )
{
b += a;
if ( b < 0 )
{
b = -b;
a = '-';
}
else
a = 0;
if ( a )
putchar ( a );
printf ( "%I64X\n", b );
}
return 0;
}

b += a;
if ( b < 0 )
{
b = -b;
a = '-';
}
else
a = 0;
if ( a )
putchar ( a )这段程序有何作用啊，我觉得没有也行啊 ，哪位牛人解释下啊，某刚出道详细点行吗？

Answer 1

%X的话会当作正数输出
所以如果b是负数，得先求相反数，然后再手动把负号补上