Update Solution.cpp

Author: yanglbme

solution/1800-1899/1870.Minimum Speed to Arrive on Time/Solution.cpp

@@ -1,24 +1,28 @@
 class Solution {
 public:
     int minSpeedOnTime(vector<int>& dist, double hour) {
-        int left = 1, right = 1e7;
-        while (left < right) {
-            int mid = (left + right) >> 1;
-            if (check(dist, mid, hour)) {
-                right = mid;
+        if (dist.size() > ceil(hour)) {
+            return -1;
+        }
+        const int m = 1e7;
+        int l = 1, r = m + 1;
+        int n = dist.size();
+        auto check = [&](int v) {
+            double s = 0;
+            for (int i = 0; i < n; ++i) {
+                double t = dist[i] * 1.0 / v;
+                s += i == n - 1 ? t : ceil(t);
+            }
+            return s <= hour;
+        };
+        while (l < r) {
+            int mid = (l + r) >> 1;
+            if (check(mid)) {
+                r = mid;
             } else {
-                left = mid + 1;
+                l = mid + 1;
             }
         }
-        return check(dist, left, hour) ? left : -1;
-    }
-
-    bool check(vector<int>& dist, int speed, double hour) {
-        double res = 0;
-        for (int i = 0; i < dist.size(); ++i) {
-            double cost = dist[i] * 1.0 / speed;
-            res += (i == dist.size() - 1 ? cost : ceil(cost));
-        }
-        return res <= hour;
+        return l > m ? -1 : l;
     }
-};
+};