refactor: non-overlapping-intervals

Author: gwbaik9717

non-overlapping-intervals/gwbaik9717.js

@@ -1,5 +1,5 @@
-// Time complexity: O(n^2)
-// Space complexity: O(n)
+// Time complexity: O(nlogn)
+// Space complexity: O(1)
 
 /**
  * @param {number[][]} intervals
@@ -14,34 +14,22 @@ var eraseOverlapIntervals = function (intervals) {
     return a[0] - b[0];
   });
 
-  const dp = Array.from({ length: intervals.length }, () => 0);
-
-  dp[0] = 1;
+  let count = 0;
+  let prevEnd = intervals[0][1];
 
   for (let i = 1; i < intervals.length; i++) {
-    const [prevStart, prevEnd] = intervals[i - 1];
-    const [currentStart, currentEnd] = intervals[i];
+    const [start, end] = intervals[i];
 
     // 구간이 겹칠 때
-    if (currentStart < prevEnd) {
-      // 현재를 포함할 때
-      let maxValue = 1;
-      for (let j = i - 1; j >= 0; j--) {
-        const [start, end] = intervals[j];
-
-        if (end <= currentStart) {
-          maxValue += dp[j];
-          break;
-        }
-      }
-
-      dp[i] = Math.max(dp[i - 1], maxValue);
+    if (prevEnd > start) {
+      count++;
+      prevEnd = Math.min(prevEnd, end);
       continue;
     }
 
     // 구간이 겹치지 않을 때
-    dp[i] = dp[i - 1] + 1;
+    prevEnd = end;
   }
 
-  return intervals.length - dp.at(-1);
+  return count;
 };