给你一个数组 `nums` ，请你完成两类查询，其中一类查询要求更新数组下标对应的值，另一类查询要求返回数组中某个范围内元素的总和。

实现 `NumArray` 类：

- `NumArray(int[] nums)` 用整数数组 `nums` 初始化对象

- `void update(int index, int val)` 将 `nums[index]` 的值更新为 `val`

- `int sumRange(int left, int right)` 返回子数组 `nums[left, right]` 的总和（即，`nums[left] + nums[left + 1], ..., nums[right]`）

**示例：**

**提示：**

- `1 <= nums.length <= 3 * 104`

- `-100 <= nums[i] <= 100`

- `0 <= index < nums.length`

- `-100 <= val <= 100`

- `0 <= left <= right < nums.length`

- 最多调用 `3 * 104` 次 `update` 和 `sumRange` 方法

**提交代码：**

class NumArray {

public class SegmentTree<E> {

private E[] tree;

private E[] data;

private Merger<E> merger;

public SegmentTree(E[] arr, Merger<E> merger){

this.merger = merger;

data = (E[])new Object[arr.length];

for(int i = 0 ; i < arr.length ; i ++)

data[i] = arr[i];

tree = (E[])new Object[4 * arr.length];

buildSegmentTree(0, 0, arr.length - 1);

}

// 在treeIndex的位置创建表示区间[l...r]的线段树

private void buildSegmentTree(int treeIndex, int l, int r){

if(l == r){

tree[treeIndex] = data[l];

return;

}

int leftTreeIndex = leftChild(treeIndex);

int rightTreeIndex = rightChild(treeIndex);

// int mid = (l + r) / 2;

int mid = l + (r - l) / 2;

buildSegmentTree(leftTreeIndex, l, mid);

buildSegmentTree(rightTreeIndex, mid + 1, r);

tree[treeIndex] = merger.merge(tree[leftTreeIndex], tree[rightTreeIndex]);

}

public int getSize(){

return data.length;

}

public E get(int index){

if(index < 0 || index >= data.length)

throw new IllegalArgumentException("Index is illegal.");

return data[index];

}

// 返回完全二叉树的数组表示中，一个索引所表示的元素的左孩子节点的索引

private int leftChild(int index){

return 2*index + 1;

}

// 返回完全二叉树的数组表示中，一个索引所表示的元素的右孩子节点的索引

private int rightChild(int index){

return 2*index + 2;

}

// 返回区间[queryL, queryR]的值

public E query(int queryL, int queryR){

if(queryL < 0 || queryL >= data.length ||

queryR < 0 || queryR >= data.length || queryL > queryR)

throw new IllegalArgumentException("Index is illegal.");

return query(0, 0, data.length - 1, queryL, queryR);

}

// 在以treeIndex为根的线段树中[l...r]的范围里，搜索区间[queryL...queryR]的值

private E query(int treeIndex, int l, int r, int queryL, int queryR){

if(l == queryL && r == queryR)

return tree[treeIndex];

int mid = l + (r - l) / 2;

// treeIndex的节点分为[l...mid]和[mid+1...r]两部分

int leftTreeIndex = leftChild(treeIndex);

int rightTreeIndex = rightChild(treeIndex);

if(queryL >= mid + 1)

return query(rightTreeIndex, mid + 1, r, queryL, queryR);

else if(queryR <= mid)

return query(leftTreeIndex, l, mid, queryL, queryR);

E leftResult = query(leftTreeIndex, l, mid, queryL, mid);

E rightResult = query(rightTreeIndex, mid + 1, r, mid + 1, queryR);

return merger.merge(leftResult, rightResult);

}

// 将index位置的值，更新为e

public void set(int index, E e){

if(index < 0 || index >= data.length)

throw new IllegalArgumentException("Index is illegal");

data[index] = e;

set(0, 0, data.length - 1, index, e);

}

// 在以treeIndex为根的线段树中更新index的值为e

private void set(int treeIndex, int l, int r, int index, E e){

if(l == r){

tree[treeIndex] = e;

return;

}

int mid = l + (r - l) / 2;

// treeIndex的节点分为[l...mid]和[mid+1...r]两部分

int leftTreeIndex = leftChild(treeIndex);

int rightTreeIndex = rightChild(treeIndex);

if(index >= mid + 1)

set(rightTreeIndex, mid + 1, r, index, e);

else // index <= mid

set(leftTreeIndex, l, mid, index, e);

tree[treeIndex] = merger.merge(tree[leftTreeIndex], tree[rightTreeIndex]);

}

@Override

public String toString(){

StringBuilder res = new StringBuilder();

res.append('[');

for(int i = 0 ; i < tree.length ; i ++){

if(tree[i] != null)

res.append(tree[i]);

else

res.append("null");

if(i != tree.length - 1)

res.append(", ");

}

res.append(']');

return res.toString();

}

}

public interface Merger<E> {

E merge(E a, E b);

}

private SegmentTree<Integer> segTree;

public NumArray(int[] nums) {

if(nums.length != 0){

Integer[] data = new Integer[nums.length];

for(int i = 0 ; i < nums.length ; i ++)

data[i] = nums[i];

segTree = new SegmentTree<>(data, (a, b) -> a + b);

}

}

public void update(int i, int val) {

if(segTree == null)

throw new IllegalArgumentException("Error");

segTree.set(i, val);

}

public int sumRange(int i, int j) {

if(segTree == null)

throw new IllegalArgumentException("Error");

return segTree.query(i, j);

}

}