62 lines
1.6 KiB
Java
62 lines
1.6 KiB
Java
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// https://en.wikipedia.org/wiki/Persistent_data_structure
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public class PersistentTree {
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public static class Node {
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Node left, right;
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int sum;
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Node(int value) {
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this.sum = value;
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}
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Node(Node left, Node right) {
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this.left = left;
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this.right = right;
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if (left != null)
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sum += left.sum;
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if (right != null)
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sum += right.sum;
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}
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}
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public static Node build(int left, int right) {
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if (left == right)
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return new Node(0);
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int mid = (left + right) >> 1;
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return new Node(build(left, mid), build(mid + 1, right));
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}
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public static int sum(int a, int b, Node root, int left, int right) {
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if (a == left && b == right)
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return root.sum;
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int mid = (left + right) >> 1;
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if (a <= mid && b > mid)
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return sum(a, Math.min(b, mid), root.left, left, mid) + sum(Math.max(a, mid + 1), b, root.right, mid + 1, right);
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else if (a <= mid)
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return sum(a, Math.min(b, mid), root.left, left, mid);
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else if (b > mid)
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return sum(Math.max(a, mid + 1), b, root.right, mid + 1, right);
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else
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throw new RuntimeException();
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}
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public static Node set(int pos, int value, Node root, int left, int right) {
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if (left == right)
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return new Node(value);
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int mid = (left + right) >> 1;
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if (pos <= mid)
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return new Node(set(pos, value, root.left, left, mid), root.right);
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else
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return new Node(root.left, set(pos, value, root.right, mid + 1, right));
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}
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// Usage example
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public static void main(String[] args) {
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int n = 10;
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Node t1 = build(0, n - 1);
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Node t2 = set(0, 1, t1, 0, n - 1);
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System.out.println(0 == sum(0, 9, t1, 0, n - 1));
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System.out.println(1 == sum(0, 9, t2, 0, n - 1));
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}
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}
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