力扣2187.完成旅途的最少时间

力扣2187.完成旅途的最少时间

朴素做法

• 二分答案

  class Solution {
      long long check(vector<int> time,long long k)
      {
          long long res=0;
          for(auto t:time)
              res += (long long)k/t;
          return res;
      }
  public:
      long long minimumTime(vector<int>& time, int totalTrips) {
          int n = time.size();
          sort(time.begin(),time.end());
          long long l=time[0]  - 1,r=(long long)totalTrips*time[0];
          while(l<r)
          {
              long long mid = l + r >> 1;
              if(check(time,mid) < (long long)totalTrips) l = mid + 1;
              else r = mid;
          }
          return l;
      }
  };

优化

• 内联函数

• 库函数min

  class Solution {
  public:
      long long minimumTime(vector<int>& time, int totalTrips) {
          //内联函数 比外部函数快一倍
          auto check = [&](long long x) -> bool
          {
              long long res=0;
              for(int t : time)
              {
                  res += x/t;
                  if(res >= totalTrips) return true;
              }
              return false;
          };
          //求最小值
          int min_t = ranges::min(time);
          long long l=min_t,r=(long long)totalTrips*min_t;
          while(l<r)
          {
              long long mid = l + r >> 1;
              //说明当前mid时res >= total
              if(check(mid)) r = mid;
              else l = mid + 1;
          }
          return r;
      }
  };