[Sehwan] Week13 solution with JavaScript

Author: nhistory

insert-interval/nhistory.js

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+var insert = function (intervals, newInterval) {
+  let result = [];
+  let i = 0;
+
+  // 1. Add all intervals before the new interval
+  while (i < intervals.length && intervals[i][1] < newInterval[0]) {
+    result.push(intervals[i]);
+    i++;
+  }
+
+  // 2. Merge all overlapping intervals with new interval
+  while (i < intervals.length && intervals[i][0] <= newInterval[1]) {
+    newInterval[0] = Math.min(newInterval[0], intervals[i][0]);
+    newInterval[1] = Math.max(newInterval[1], intervals[i][1]);
+    i++;
+  }
+  result.push(newInterval);
+
+  // 3. Add all intervals after the new interval
+  while (i < intervals.length && intervals[i][1] >= newInterval[0]) {
+    result.push(intervals[i]);
+    i++;
+  }
+
+  return result;
+};
+
+// TC = O(n)
+// SC = O(n)

meeting-rooms-ii/nhistory.js

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+class Solution {
+  /**
+   * @param {Interval[]} intervals
+   * @returns {number}
+   */
+  minMeetingRooms(intervals) {
+    // Edge case
+    if (intervals.length === 0) return 0;
+
+    let startTimes = intervals.map((interval) => interval.start);
+    let endTimes = intervals.map((interval) => interval.end);
+
+    startTimes.sort((a, b) => a - b);
+    endTimes.sort((a, b) => a - b);
+
+    let roomNeeded = 0;
+    let endIndex = 0;
+
+    for (let i = 0; i < intervals.length; i++) {
+      if (startTimes[i] < endTimes[endIndex]) roomNeeded++;
+      else endIndex++;
+    }
+
+    return roomNeeded;
+  }
+}
+
+// TC: O(nlogn)
+// SC: O(n)

merge-intervals/nhistory.js

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+var merge = function (intervals) {
+  // Sort intervals with first start number
+  intervals.sort((a, b) => a[0] - b[0]);
+  let result = [];
+  let currentInterval = intervals[0];
+
+  for (let i = 1; i < intervals.length; i++) {
+    if (currentInterval[1] >= intervals[i][0]) {
+      currentInterval[1] = Math.max(currentInterval[1], intervals[i][1]);
+    } else {
+      result.push(currentInterval);
+      currentInterval = intervals[i];
+    }
+  }
+
+  result.push(currentInterval);
+
+  return result;
+};
+
+// TC: O(nlogn)
+// SC: O(n)

non-overlapping-intervals/nhistory.js

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+var eraseOverlapIntervals = function (intervals) {
+  let count = 0;
+  intervals.sort((a, b) => a[1] - b[1]);
+  let currentEnd = intervals[0][1];
+
+  for (let i = 1; i < intervals.length; i++) {
+    if (currentEnd > intervals[i][0]) {
+      count++;
+    } else {
+      currentEnd = intervals[i][1];
+    }
+  }
+
+  return count;
+};
+
+// TC: O(nlogn)
+// SC: O(1)

rotate-image/nhistory.js

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+var rotate = function (matrix) {
+  let top = 0,
+    bottom = matrix.length - 1;
+  let left, right;
+
+  while (top < bottom) {
+    (left = top), (right = bottom);
+
+    for (let i = 0; i < bottom - top; i++) {
+      const topLeft = matrix[top][left + i];
+      matrix[top][left + i] = matrix[bottom - i][left];
+      matrix[bottom - i][left] = matrix[bottom][right - i];
+      matrix[bottom][right - i] = matrix[top + i][right];
+      matrix[top + i][right] = topLeft;
+    }
+
+    top++;
+    bottom--;
+  }
+};
+
+// TC: O(n^2)
+// SC: O(1)