HDU 4510 小Q系列故事——为什么时光不能倒流

这道题很水的，记得ACM刚入门的时候，做过类似的题目，相当于加减法的模拟

代码：

#include <cstdio>
int HH, MM, SS, hh, mm, ss, T;
int main ( ) {
    scanf ( "%d", &T );
        while ( T-- ) {
            scanf ( "%d:%d:%d", &HH, &MM, &SS );
            scanf ( "%d:%d:%d", &hh, &mm, &ss );
            if ( SS >= ss ) SS -= ss;
            else {
                MM--;
                SS = (SS + 60 - ss);
            }
            if ( MM >= mm ) MM -= mm;
            else {
                H--;
                MM = MM + 60 - mm;
            }
            if ( HH >= hh ) HH -= hh;
            else {
                HH = HH - hh + 12;
            }
	    HH %= 12;
	    HH = (HH+12)%12;
            printf ( "%.2d:%.2d:%.2d\n", HH, MM, SS );
        }
}