Added H Index

Author: ryanoneill

src/h_index.rs

@@ -0,0 +1,65 @@
+/// Given an array of integers `citations` where `citations[i]` is the number
+/// of citations a researcher received for their `ith` paper, return the
+/// researcher's h-index.
+///
+/// According to the definition of h-index on Wikipedia: The h-index is defined
+/// as the maximum value of `h` such that the given researcher has published
+/// at least `h` papers that have each been cited at least `h` times.
+struct Solution;
+
+impl Solution {
+
+    pub fn h_index(citations: Vec<i32>) -> i32 {
+        let n = citations.len();
+        let mut times = vec![0; n+1];
+
+        for cite in citations {
+            let value = (cite as usize).min(n);
+            times[value] += 1;
+        }
+
+        let mut count = 0;
+        let mut index = n;
+        let mut result = 0;
+
+        while index > 0 {
+            let value = times[index];
+            count += value;
+            if count >= index {
+                result = index as i32;
+                break;
+            }
+            index -= 1;
+        }
+
+        result
+    }
+
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Solution;
+
+    #[test]
+    fn example_1() {
+        let citations = vec![3,0,6,1,5];
+        let result = Solution::h_index(citations);
+        assert_eq!(result, 3);
+    }
+
+    #[test]
+    fn example_2() {
+        let citations = vec![1,3,1];
+        let result = Solution::h_index(citations);
+        assert_eq!(result, 1);
+    }
+
+    #[test]
+    fn real_world_1() {
+        let citations = vec![4,4,0,0];
+        let result = Solution::h_index(citations);
+        assert_eq!(result, 2);
+    }
+
+}

src/lib.rs

@@ -119,6 +119,8 @@ pub mod graph_valid_tree; // 261
 
 pub mod closest_binary_search_tree_value; // 270
 
+pub mod h_index; // 274 ✓
+
 pub mod move_zeroes; // 283
 
 pub mod find_median_from_data_stream; // 295