20240904 finished.

src/problem/mod.rs

@@ -225,3 +225,4 @@ mod p3127_make_a_square_with_the_same_color;
 mod p1450_number_of_students_doing_homework_at_a_given_time;
 mod p2024_maximize_the_confusion_of_an_exam;
 mod p2708_maximum_strength_of_a_group;
+mod p2860_happy_students;

src/problem/p2860_happy_students.rs

@@ -0,0 +1,46 @@
+/**
+ * [2860] Happy Students
+ */
+pub struct Solution {}
+
+
+// submission codes start here
+
+impl Solution {
+    pub fn count_ways(nums: Vec<i32>) -> i32 {
+        let mut nums: Vec<usize> = nums.iter().map(|x| *x as usize).collect();
+        let n = nums.len();
+        nums.sort();
+
+        // 是否能不选中任何学生
+        let mut result = 0; 
+
+        for i in 0..=n {
+            if i > 0 && nums[i - 1] >= i {
+                continue;
+            } 
+            
+            if i < n && nums[i] <= i {
+                continue;
+            }
+            
+            result += 1;
+        }
+
+        result
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_2860() {
+        assert_eq!(2, Solution::count_ways(vec![1, 1]));
+        assert_eq!(3, Solution::count_ways(vec![6, 0, 3, 3, 6, 7, 2, 7]));
+        assert_eq!(1, Solution::count_ways(vec![1, 0, 1, 1]));
+    }
+}