Add problem 0278: First Bad Version

src/lib.rs

@@ -277,6 +277,7 @@ pub mod problem_0260_single_number_iii;
 pub mod problem_0268_missing_number;
 pub mod problem_0274_h_index;
 pub mod problem_0275_h_index_ii;
+pub mod problem_0278_first_bad_version;
 pub mod problem_0283_move_zeroes;
 pub mod problem_0290_word_pattern;
 pub mod problem_0299_bulls_and_cows;

src/problem_0278_first_bad_version/binary_search.rs

@@ -0,0 +1,44 @@
+use super::Solution as _;
+
+pub struct Solution {
+    bad: i32,
+}
+
+impl Solution {
+    pub fn first_bad_version(&self, n: i32) -> i32 {
+        let mut left = 1;
+        let mut right = n;
+        while left < right {
+            let mid = (right - left) / 2 + left;
+            if self.isBadVersion(mid) {
+                right = mid;
+            } else {
+                left = mid + 1;
+            }
+        }
+        right
+    }
+}
+
+impl super::Solution for Solution {
+    fn new(bad: i32) -> Self {
+        Self { bad }
+    }
+
+    #[allow(non_snake_case)] // Expected.
+    fn isBadVersion(&self, version: i32) -> bool {
+        version >= self.bad
+    }
+
+    fn first_bad_version(&self, n: i32) -> i32 {
+        self.first_bad_version(n)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_solution() {
+        super::super::tests::run::<super::Solution>();
+    }
+}

src/problem_0278_first_bad_version/mod.rs

@@ -0,0 +1,23 @@
+pub mod binary_search;
+
+pub trait Solution {
+    fn new(bad: i32) -> Self;
+
+    #[allow(non_snake_case)] // Expected.
+    fn isBadVersion(&self, version: i32) -> bool;
+
+    fn first_bad_version(&self, n: i32) -> i32;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Solution;
+
+    pub fn run<S: Solution>() {
+        let test_cases = [((5, 4), 4), ((1, 1), 1)];
+
+        for ((n, bad), expected) in test_cases {
+            assert_eq!(S::new(bad).first_bad_version(n), expected);
+        }
+    }
+}