判断 Gym 100502K Train Passengers

题目传送门

 /*
     题意：几个判断，车上的人不能 <0 或 > C；车上初始和结束都不能有人在 (为0)；车上满员时才有等候的人
     水题：难点在于读懂题目意思，状态不佳，一直没搞懂意思，在这题卡住了
         主要要理解have to wait 的意思
 */
 #include <cstdio>
 #include <iostream>
 #include <algorithm>
 #include <cstring>
 #include <string>
 #include <cmath>
 #include <set>
 #include <map>
 #include <queue>
 using namespace std;

 const int MAXN = 1e2 + ;
 const int INF = 0x3f3f3f3f;
 int l[MAXN], e[MAXN], w[MAXN];

 int main(void)        //Gym 100502K Train Passengers
 {
     //freopen ("K.in", "r", stdin);

     int C, n;

     while (scanf ("%d%d", &C, &n) == )
     {
         int i;
         for (i=; i<=n; ++i)
         {
             scanf ("%d%d%d", &l[i], &e[i], &w[i]);
         }
         long long sum = ;
         for (i=; i<=n; ++i)
         {
             if (i == n && w[i] > )    {puts ("impossible");    break;};
             sum -= l[i];
             if (sum <  || sum > C)    {puts ("impossible");    break;};
             sum += e[i];
             if (sum <  || sum > C)    {puts ("impossible");    break;};
             if (w[i] >  && sum < C)    {puts ("impossible");    break;};        //当时没理解题意，写不出来:)
         }

         if (i > n)
         {
             if (sum != )    puts ("impossible");
             else    puts ("possible");
         }
     }

     return ;
 }

 /*
 impossible
 possible
 */