Another problem done with Rust

1394/main.rs

@@ -0,0 +1,27 @@
+use std::collections::HashMap;
+
+pub fn find_lucky(arr: Vec<i32>) -> i32 {
+    let mut hm = HashMap::<i32, i32>::new();
+    for n in arr {
+        let entry = hm.entry(n).or_insert(0);
+        *entry += 1;
+    }
+    let mut lucky = Vec::new(); 
+    for (k, v) in hm {
+        if k == v {
+            lucky.push(k);
+        }
+    }
+    let mut max = -1;
+    for n in lucky {
+        if n > max {
+            max = n;
+        }
+    }
+    return max;
+}
+
+pub fn main() {
+    println!("Expected: 4");
+    println!("Got: {}", find_lucky(vec![1, 4, 4, 4, 4, 2, 6]));
+}

1394/problem.txt

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+Given an array of integers arr, a lucky integer is an integer which has a frequency in the array equal to its value.
+
+Return a lucky integer in the array. If there are multiple lucky integers return the largest of them. If there is no lucky integer return -1.
+
+Example 1:
+
+Input: arr = [2,2,3,4]
+Output: 2
+Explanation: The only lucky number in the array is 2 because frequency[2] == 2.
+
+Example 2:
+
+Input: arr = [1,2,2,3,3,3]
+Output: 3
+Explanation: 1, 2 and 3 are all lucky numbers, return the largest of them.
+
+Example 3:
+
+Input: arr = [2,2,2,3,3]
+Output: -1
+Explanation: There are no lucky numbers in the array.
+
+Example 4:
+
+Input: arr = [5]
+Output: -1
+
+Example 5:
+
+Input: arr = [7,7,7,7,7,7,7]
+Output: 7
+
+Constraints:
+
+    1 <= arr.length <= 500
+    1 <= arr[i] <= 500

1394/run.sh

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+#!/bin/bash
+
+rustc main.rs
+./main
+rm main