lazy 线段树代码

 1 class Node {
 2     int l, r;
 3     int sum;
 4     int lazy;
 5 }
 6 
 7 class SegmentTree {
 8 
 9     private Node[] tree;
10 
11     private int[] nums;
12 
13     public SegmentTree(int[] nums) {
14         int n = nums.length;
15         this.nums = nums;
16         tree = new Node[n << 2];
17         for (int i = 0; i < tree.length; i++) {
18             tree[i] = new Node();
19         }
20         build(1, 1, n);
21     }
22 
23 
24     public void build(int node, int left, int right) {
25         tree[node].l = left;
26         tree[node].r = right;
27         if (left == right) {
28             tree[node].sum = nums[left - 1];
29             return;
30         }
31         int mid = (left + right) >> 1;
32         build(node << 1, left, mid);
33         build(node << 1 | 1, mid + 1, right);
34         pushUp(node);
35     }
36 
37     public void pushUp(int node) {
38         tree[node].sum = tree[node << 1].sum + tree[node << 1 | 1].sum;
39     }
40 
41     public void modify(int node, int left, int right) {
42         // 修改区间大于该节点区间范围
43         if (tree[node].l >= left && tree[node].r <= right) {
44             tree[node].sum += tree[node].r - tree[node].l + 1;
45             tree[node].lazy ^= 1;
46             return;
47         }
48         pushDown(node);
49 
50         int mid = (tree[node].l + tree[node].r) >> 1;
51         if (left <= mid) {
52             modify(node << 1, left, right);
53         }
54         if (right > mid) {
55             modify(node << 1 | 1, left, right);
56         }
57         pushUp(node);
58     }
59 
60     public void pushDown(int node) {
61         if (tree[node].lazy == 1) {
62             int mid = (tree[node].l + tree[node].r) >> 1;
63             tree[node << 1].sum += mid - tree[node << 1].l + 1;
64             tree[node << 1].lazy ^= 1;
65             tree[node << 1 | 1].sum += tree[node << 1 | 1].r - mid;
66             tree[node << 1 | 1].lazy ^= 1;
67             tree[node].lazy ^= 1;
68         }
69     }
70 
71     public int query(int node, int left, int right) {
72         if (tree[node].l >= left && tree[node].r <= right) {
73             return tree[node].sum;
74         }
75         pushDown(node);
76         int mid = (tree[node].l + tree[node].r) >> 1;
77         int res = 0;
78         if (left <= mid) {
79             res += query(node << 1, left, right);
80         }
81         if (right > mid) {
82             res += query(node << 1 | 1, left, right);
83         }
84         return res;
85     }
86 
87 }
88 
89 class Solution{
90     public static void main(String[] args) {
91         int[] nums = {5,6,7,8};
92         SegmentTree segmentTree = new SegmentTree(nums);
93         segmentTree.modify(1, 1, 3);
94         int res = segmentTree.query(1, 2, 4);
95         System.out.println(res);
96 
97     }
98 }