problem 1110

分别记Spot、Puff、Yertle的年龄为a1、a2、a3。由题意列方程组：
①a1 = s + a2 + b1(Spot was s years old when Puff was born)
②a2 = p + a3 + b2(Puff was p years old when Yertle was born)
③a1 = y + a3 + b3(Spot was y years old when Yertle was born)
④a1 + a2 + a3 = 12 + j(The sum of Spot's age, Puff's age, and Yertle's age equals the sum of Dick's age (12) and Jane's age (j))
其中b1,b2,b3为待定常数，它们只能取0或1。枚举b1, b2, b3即可。 

#include<stdio.h>
int s,p,y,j;
bool solve(int b1, int b2, int b3)
{
    int a1 = 0, a2 = 0, a3 = 0;
    if(y + b3 == s + p + b1 + b2)
    {
        a2 = j - s - b1 + p + b2;
        if(a2 % 3 == 0)
        {
            a2 = a2 / 3;
            a1 = s + a2 + b1;
            a3 = a2 - p - b2;
            if(a1 + a2 + a3 == j)
            {
                printf("%d %d %d/n", a1, a2, a3);
                return true;
            }
        }
    }
    return false;
}
int main()
{
#ifndef ONLINE_JUDGE
    freopen("1110.txt","r",stdin);
#endif
    while(scanf("%d%d%d%d",&s,&p,&y,&j)!=EOF)
    {
        j += 12;
        if(solve(0, 0, 0) || solve(0, 0, 1) || 
           solve(0, 1, 0) || solve(0, 1, 1) || 
           solve(1, 0, 0) || solve(1, 0, 1) || 
           solve(1, 1, 0) || solve(1, 1, 1));
    }
#ifndef ONLINE_JUDGE
    fclose(stdin);
#endif
    return 0;
}