Solve leetcode 875

src/lc875.rs

@@ -0,0 +1,77 @@
+#[cfg(test)]
+use std::cmp::Ordering;
+
+#[cfg(test)]
+struct Solution;
+
+#[cfg(test)]
+impl Solution {
+    pub fn min_eating_speed(piles: Vec<i32>, h: i32) -> i32 {
+        if piles.len() == 1 {
+            return (piles[0] as f64 / h as f64).ceil() as i32;
+        }
+        match piles.len().cmp(&(h as usize)) {
+            Ordering::Less => binary_search(h, *piles.iter().max().unwrap(), &piles),
+            Ordering::Equal => *piles.iter().max().unwrap(),
+            Ordering::Greater => panic!("can't eat that many bananas in such short amount of time")
+        }
+    }
+}
+
+#[cfg(test)]
+fn binary_search(h: i32, max: i32, piles: &[i32]) -> i32 {
+    let (mut i, mut j) = (1, max);
+    loop {
+        let x = (i + j) as f64 / 2f64;
+        let d = x.floor();
+        match piles.iter().fold(0i64, |a, b| { a + (*b as f64 / d).ceil() as i64 }).cmp(&(h as i64)) {
+            Ordering::Equal | Ordering::Less => {
+                // try to find a lower m, or break if its impossible
+                if i == j {
+                    break;
+                }
+                j = x.floor() as i32;
+            }
+            Ordering::Greater => {
+                // try to find a greater m
+                if i == j {
+                    break;
+                }
+                i = x.ceil() as i32;
+            }
+        }
+    }
+    i
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_min_eating_speed() {
+        let res = Solution::min_eating_speed(vec![3, 6, 7, 11], 8);
+        assert_eq!(res, 4);
+
+        let res = Solution::min_eating_speed(vec![30, 11, 23, 4, 20], 5);
+        assert_eq!(res, 30);
+
+        let res = Solution::min_eating_speed(vec![30, 11, 23, 4, 20], 6);
+        assert_eq!(res, 23);
+
+        let res = Solution::min_eating_speed(
+            vec![332484035, 524908576, 855865114, 632922376, 222257295, 690155293, 112677673, 679580077, 337406589, 290818316, 877337160, 901728858, 679284947, 688210097, 692137887, 718203285, 629455728, 941802184],
+            823855818,
+        );
+        assert_eq!(res, 14);
+
+        let res = Solution::min_eating_speed(vec![1000000000], 2);
+        assert_eq!(res, 500000000);
+
+        let res = Solution::min_eating_speed(vec![312884470], 312884469);
+        assert_eq!(res, 2);
+
+        let res = Solution::min_eating_speed(vec![1000000000, 1000000000], 3);
+        assert_eq!(res, 1000000000)
+    }
+}

src/lib.rs

@@ -6,6 +6,6 @@ pub mod lc143;
 pub mod lc206;
 pub mod lc22;
 pub mod lc739;
-
 pub mod lc572;
 pub mod lc853;
+pub mod lc875;