algoexpert.io - Disk_Stacking

Author: Partho Biswas

algoexpert.io/python/Disk_Stacking.py

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+
+
+# O(n^2) time | O(n) space
+def diskStacking(disks):
+    disks.sort(key = lambda disk: disks[2])
+    heights = [disks[2] for disk in disks]
+    sequences = [None for disk in disks]
+    maxHeightIndex = 0
+    for i in range(1, len(disks)):
+        currentDisk = disks[i]
+        for j in range(0, i):
+            otherDisk = disks[j]
+            if areValidDimensions(otherDisk, currentDisk):
+                if heights[i] <= currentDisk[2] + heights[j]:
+                    heights[i] = currentDisk[2] + heights[j]
+                    sequences[i] = j
+        if heights[i] >= heights[maxHeightIndex]
+            maxHeightIndex = i
+    return buildSequence(disks, sequences, maxHeightIndex)
+
+
+def areValidDimensions(other, current):
+    return other[0] < current[0] and other[1] < current[1] and other[2] < current[2]
+
+
+def buildSequence(array, sequences, currentIndex):
+    sequence = []
+    while currentIndex is not None:
+        sequence.append(array[currentIndex])
+        currentIndex = sequences[currentIndex]
+    return list(reversed(sequence))