72: See solutions

72-non-overlapping-intervals/src/lib.rs

@@ -1,47 +1,17 @@
-use std::collections::HashSet;
+pub fn erase_overlap_intervals(mut intervals: Vec<Vec<i32>>) -> i32 {
+    intervals.sort_unstable_by_key(|interval| interval[1]);
 
-pub fn erase_overlap_intervals(intervals: Vec<Vec<i32>>) -> i32 {
-    let intervals_len = intervals.len();
-    let unique_intervals: HashSet<_> = intervals.into_iter().collect();
+    let mut removed = 0;
+    let mut current_end = intervals[0][1];
 
-    let mut removed = (intervals_len - unique_intervals.len()) as i32;
-
-    let mut overlapped_counts = vec![0; unique_intervals.len()];
-    let mut overlapped_indices = vec![vec![]; unique_intervals.len()];
-
-    for (i, interval1) in unique_intervals.iter().enumerate() {
-        for (j, interval2) in unique_intervals.iter().enumerate().skip(i + 1) {
-            if (interval1[0] <= interval2[0] && interval2[0] < interval1[1])
-                || (interval1[0] < interval2[1] && interval2[1] <= interval1[1])
-            {
-                overlapped_counts[i] += 1;
-                overlapped_counts[j] += 1;
-                overlapped_indices[i].push(j);
-                overlapped_indices[j].push(i);
-            }
+    for interval in intervals.iter().skip(1) {
+        if interval[0] < current_end {
+            removed += 1;
+        } else {
+            current_end = interval[1];
         }
     }
 
-    loop {
-        println!("{:?}", overlapped_counts);
-        let (max_idx, count) = overlapped_counts
-            .iter_mut()
-            .enumerate()
-            .max_by(|(_, cnt1), (_, cnt2)| cnt1.cmp(cnt2))
-            .unwrap();
-
-        if *count == 0 {
-            break;
-        }
-
-        *count = 0;
-        for idx in overlapped_indices[max_idx].iter() {
-            overlapped_counts[*idx] -= 1;
-        }
-
-        removed += 1
-    }
-
     removed
 }
 
@@ -93,4 +63,18 @@ mod tests {
             4
         );
     }
+
+    #[test]
+    fn failed_case3() {
+        assert_eq!(
+            erase_overlap_intervals(vec![
+                vec![0, 2],
+                vec![1, 3],
+                vec![2, 4],
+                vec![3, 5],
+                vec![4, 6]
+            ]),
+            2
+        );
+    }
 }