Create Segment tree.js

trees/Segment tree.js

@@ -0,0 +1,379 @@
+package main
+
+
+import (
+
+"bufio"
+
+"fmt"
+
+"os"
+
+"strconv"
+
+"strings"
+
+)
+
+
+type SegmentTreeData struct {
+
+prefix int
+
+suffix int
+
+best   int
+
+total  int
+
+}
+
+
+func createData(value int) SegmentTreeData {
+
+return SegmentTreeData{
+
+
+prefix: value,
+
+suffix: value,
+
+best:   value,
+
+total:  value,
+
+}
+
+}
+
+
+func merge(left, right SegmentTreeData) SegmentTreeData {
+
+total := left.total + right.total
+
+prefix := max(left.prefix, left.total+right.prefix)
+
+suffix := max(right.suffix, right.total+left.suffix)
+
+best := max(
+
+left.best,
+
+right.best,
+
+prefix,
+
+suffix,
+
+left.suffix+right.prefix,
+
+)
+
+
+return SegmentTreeData{
+
+prefix,
+
+suffix,
+
+best,
+
+total,
+
+}
+
+}
+
+
+type SegmentTree struct {
+
+n    int
+
+data []SegmentTreeData
+
+}
+
+
+func Build(arr []int) *SegmentTree {
+
+n := len(arr)
+
+length := n * 4
+
+data := make([]SegmentTreeData, length)
+
+tree := &SegmentTree{
+
+n,
+
+data,
+
+}
+
+tree.build(arr, 1, 1, n)
+
+
+
+return tree
+
+}
+
+
+func (tree *SegmentTree) build(arr []int, index int, left int, right int) {
+
+if left > right {
+
+return
+
+} else if left == right {
+
+tree.data[index] = createData(arr[left-1])
+
+} else {
+
+middle := (left + right) / 2
+
+
+tree.build(arr, index*2, left, middle)
+
+tree.build(arr, index*2+1, middle+1, right)
+
+tree.data[index] = merge(tree.data[index*2], tree.data[index*2+1])
+
+}
+
+}
+
+
+func (tree *SegmentTree) Update(x, y int) {
+
+
+tree.update(1, 1, tree.n, x, y)
+
+}
+
+
+func (tree *SegmentTree) update(index int, left int, right int, updateIndex int, updateValue int) {
+
+if left > right || left > updateIndex || right < updateIndex {
+
+return
+
+} else if left == right {
+
+tree.data[index] = createData(updateValue)
+
+} else {
+
+middle := (left + right) / 2
+
+
+tree.update(index*2, left, middle, updateIndex, updateValue)
+
+tree.update(index*2+1, middle+1, right, updateIndex, updateValue)
+
+tree.data[index] = merge(tree.data[index*2], tree.data[index*2+1])
+
+
+}
+
+}
+
+
+func (tree *SegmentTree) Find(x, y int) int {
+
+return tree.find(1, 1, tree.n, x, y).best
+
+}
+
+
+func (tree *SegmentTree) find(index int, left int, right int, findLeft int, findRight int) SegmentTreeData {
+
+if left == findLeft && right == findRight {
+
+return tree.data[index]
+
+} else {
+
+middle := (left + right) / 2
+
+
+if findRight <= middle {
+
+return tree.find(index*2, left, middle, findLeft, findRight)
+
+} else if findLeft > middle {
+
+return tree.find(index*2+1, middle+1, right, findLeft, findRight)
+
+} else {
+
+
+leftResult := tree.find(index*2, left, middle, findLeft, min(middle, findRight))
+
+rightResult := tree.find(index*2+1, middle+1, right, max(findLeft, middle+1), findRight)
+
+mergedResult := merge(leftResult, rightResult)
+
+return mergedResult
+
+}
+
+}
+
+}
+
+
+func max(x int, rest ...int) int {
+
+mx := x
+
+
+for _, value := range rest {
+
+if mx < value {
+
+mx = value
+
+}
+
+}
+
+
+return mx
+
+
+}
+
+
+func min(x int, rest ...int) int {
+
+mn := x
+
+
+for _, value := range rest {
+
+if mn > value {
+
+mn = value
+
+}
+
+}
+
+
+return mn
+
+}
+
+
+var reader *bufio.Reader = bufio.NewReader(os.Stdin)
+
+var writer *bufio.Writer = bufio.NewWriter(os.Stdout)
+
+
+func readInt() int {
+
+var value int
+
+fmt.Fscanf(reader, "%d\n", &value)
+
+
+
+return value
+
+}
+
+
+func writeInt(value int) {
+
+fmt.Fprintln(writer, value)
+
+}
+
+
+func readArray(n int) []int {
+
+line, err := reader.ReadString('\n')
+
+if err != nil {
+
+panic(err)
+
+}
+
+
+stringArray := strings.Split(strings.TrimSpace(line), " ")
+
+if len(stringArray) != n {
+
+panic(fmt.Errorf("Expected input array to be of size %d, but was %d", n, len(stringArray)))
+
+}
+
+
+arr := make([]int, n)
+
+for i := 0; i < n; i++ {
+
+value, err := strconv.Atoi(stringArray[i])
+
+if err != nil {
+
+panic(err)
+
+}
+
+
+arr[i] = value
+
+}
+
+
+return arr
+
+}
+
+
+func main() {
+
+defer writer.Flush()
+
+
+n := readInt()
+
+arr := readArray(n)
+
+tree := Build(arr)
+
+
+m := readInt()
+
+for i := 0; i < m; i++ {
+
+
+query := readArray(3)
+
+t := query[0]
+
+x := query[1]
+
+y := query[2]
+
+
+if t == 0 {
+
+tree.Update(x, y)
+
+} else {
+
+value := tree.Find(x, y)
+
+writeInt(value)
+
+}
+
+}
+
+}
+