Update Solution.rs

Author: yanglbme

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

@@ -1,33 +1,31 @@
 impl Solution {
     pub fn min_speed_on_time(dist: Vec<i32>, hour: f64) -> i32 {
+        if dist.len() as f64 > hour.ceil() {
+            return -1;
+        }
+        const M: i32 = 10_000_000;
+        let (mut l, mut r) = (1, M + 1);
         let n = dist.len();
-
-        let check = |speed| {
-            let mut cur = 0.0;
-            for (i, &d) in dist.iter().enumerate() {
-                if i == n - 1 {
-                    cur += (d as f64) / (speed as f64);
-                } else {
-                    cur += ((d as f64) / (speed as f64)).ceil();
-                }
+        let check = |v: i32| -> bool {
+            let mut s = 0.0;
+            for i in 0..n {
+                let t = dist[i] as f64 / v as f64;
+                s += if i == n - 1 { t } else { t.ceil() };
             }
-            cur <= hour
+            s <= hour
         };
-
-        let mut left = 1;
-        let mut right = 1e7 as i32;
-        while left < right {
-            let mid = left + (right - left) / 2;
-            if !check(mid) {
-                left = mid + 1;
+        while l < r {
+            let mid = (l + r) / 2;
+            if check(mid) {
+                r = mid;
             } else {
-                right = mid;
+                l = mid + 1;
             }
         }
-
-        if check(left) {
-            return left;
+        if l > M {
+            -1
+        } else {
+            l
         }
-        -1
     }
 }