rs: add «3075. Maximize Happiness of Selected Children»

Signed-off-by: Matej Focko <me@mfocko.xyz>

rs/maximize-happiness-of-selected-children.rs

@@ -0,0 +1,18 @@
+use std::cmp;
+use std::collections::BinaryHeap;
+
+impl Solution {
+    pub fn maximum_happiness_sum(happiness: Vec<i32>, k: i32) -> i64 {
+        let mut q: BinaryHeap<i32> = BinaryHeap::from(happiness);
+
+        let mut happiness: i64 = 0;
+
+        let k: i64 = k.into();
+        for i in 0..k {
+            let next: i64 = q.pop().expect("k is smaller than length").into();
+            happiness += cmp::max(0, next - i);
+        }
+
+        happiness
+    }
+}