SegmentTree add set().

09-Segment-Tree/01-Segment-Tree-Basics/src/SegmentTree.java

@@ -90,6 +90,35 @@ else if (queryR <= mid)
  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);
+ }
+
+ 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;
+ 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();