HZAU 1018 Catching Dogs

题目连接
模拟

#include<iostream>
 #include<cstdio>
 #include<cmath>
 using namespace std;
 const int maxn = 10 + 10;
 int n, v0;
 int v[maxn];
 double p[maxn];
 void solve()
 {
  double p0 = 0;
  double ans = 0;
  for(int i = 0; i < n; i++)
    scanf("%lf%d", &p[i], &v[i]);
  bool flag = true;
  for(int i = 0; i < n; i++){
    if (v[i] == 0)
    {
      double t = abs(p0 - p[i])/v0;
      ans += t;
      p0 = p[i];
      for(int j = i + 1; j < n; j++)
        p[j] += (v[j] * t);
      continue;
    }
    int s;
    if(p[i] == p0) s = 0;
    else if((p[i] - p0) * v[i] > 0) s = 1; // zhuiji
    else s = 2; //xiangyu
    if(s == 1 && abs(v[i]) >= v0) {flag = false; break;}
    double t;
    if(s == 1)
    {
      t = abs(p0 - p[i]) / (v0 - abs(v[i]));
      p0 += (v[i]/abs(v[i]) * t * v0);
    }
    else if(s == 2)
    {
      t = abs(p0 - p[i]) / (v0 + abs(v[i]));
      p0 -= (v[i]/abs(v[i]) * t * v0);
    }
    else t = 0;
    ans += t;
    for(int j = i + 1; j < n; j++)
      p[j] += (v[j] * t);
  }
  if(flag) printf("%.2lf\n", ans);
  else printf("Bad Dog\n");
 }
 int main(){
 //freopen("input.txt", "r", stdin);
  while(scanf("%d%d", &n, &v0) != EOF)
    solve();
 }