CF-1117C-Magic Ship

• 二分

  C - Magic Ship

  GNU C++11

  Accepted

  31 ms

  1700 KB

  #include "bits/stdc++.h"
  using namespace std;
  typedef long long LL;
  typedef pair<LL, LL> PLL;
  const int MAXN = 1e5 + 5;
  PLL arr[MAXN];
  char s[MAXN];
  int main() {
      int n; 
      LL x1, x2, y1, y2;
      scanf("%lld%lld%lld%lld", &x1, &y1, &x2, &y2);
      scanf("%d%s", &n, s + 1);
      for (int i = 1; i <= n; i++) {
          arr[i] = arr[i - 1];
          switch(s[i]) {
              case 'U' : arr[i].second++; break;
              case 'D' : arr[i].second--; break;
              case 'L' : arr[i].first--; break;
              case 'R' : arr[i].first++; break;
          }
      }
      LL l = 0, r = 3e14, mid;
      while (r - l > 1) {
          mid = l + r >> 1;
          LL x, y;
          // 求出船不动任风吹mid天之后的船的坐标 
          x = x1 + mid / n * arr[n].first + arr[mid % n].first;
          y = y1 + mid / n * arr[n].second + arr[mid % n].second;
          // 如果距离终点mid以内，那么每天一步可以到达，否则无法到达 
          if (abs(y - y2) + abs(x - x2) <= mid) {
              r = mid;
          } else {
              l = mid;
          }
      }
      printf("%lld\n", r == 3e14 ? -1 : r);
      return 0;
  }