Precise DOM morphing
morphing
typescript
dom
Optimize LIS reconstruction in child reordering
Use pre-sized LIS buffers and Int32Array predecessor tracking to reduce allocations and avoid unshift-heavy reconstruction in the reordering hot path while preserving behavior.
+18
-29
+18
-29
src/morphlex.ts
+18
-29
src/morphlex.ts
···
946
946
const n = sequence.length
947
947
if (n === 0) return []
948
948
949
-
// smallestEnding[i] = smallest ending value of any increasing subsequence of length i+1
950
-
const smallestEnding: Array<number> = []
951
-
// indices[i] = index in sequence where smallestEnding[i] occurs
952
-
const indices: Array<number> = []
953
-
// prev[i] = previous index in the LIS ending at sequence[i]
954
-
const prev: Array<number> = new Array(n)
949
+
const smallestEnding = new Array<number>(n)
950
+
const indices = new Array<number>(n)
951
+
const prev = new Int32Array(n)
952
+
prev.fill(-1)
955
953
956
-
// Build the LIS by processing each value
954
+
let lisLength = 0
955
+
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for (let i = 0; i < n; i++) {
958
957
const val = sequence[i]
959
-
if (val === undefined) continue // Skip new nodes (not in original sequence)
958
+
if (val === undefined) continue
960
959
961
-
// Binary search: find where this value fits in smallestEnding
962
960
let left = 0
963
-
let right = smallestEnding.length
961
+
let right = lisLength
964
962
965
963
while (left < right) {
966
964
const mid = Math.floor((left + right) / 2)
···
968
966
else right = mid
969
967
}
970
968
971
-
// Link this element to the previous one in the subsequence
972
969
prev[i] = left > 0 ? indices[left - 1]! : -1
973
970
974
-
// Either extend the sequence or update an existing position
975
-
if (left === smallestEnding.length) {
976
-
// Extend: this value is larger than all previous endings
977
-
smallestEnding.push(val)
978
-
indices.push(i)
979
-
} else {
980
-
// Update: found a better (smaller) ending for this length
981
-
smallestEnding[left] = val
982
-
indices[left] = i
983
-
}
971
+
smallestEnding[left] = val
972
+
indices[left] = i
973
+
if (left === lisLength) lisLength++
984
974
}
985
975
986
-
// Reconstruct the actual indices that form the LIS
987
-
const result: Array<number> = []
988
-
if (indices.length === 0) return result
976
+
if (lisLength === 0) return []
977
+
978
+
const result = new Array<number>(lisLength)
979
+
let curr = indices[lisLength - 1]!
989
980
990
-
// Walk backwards through prev links to build the LIS
991
-
let curr: number | undefined = indices[indices.length - 1]
992
-
while (curr !== undefined && curr !== -1) {
993
-
result.unshift(curr)
994
-
curr = prev[curr]
981
+
for (let i = lisLength - 1; i >= 0; i--) {
982
+
result[i] = curr
983
+
curr = prev[curr]!
995
984
}
996
985
997
986
return result