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Code05_TreeMaxWidth.java
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114 lines (103 loc) · 2.65 KB
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package class11;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.Queue;
public class Code05_TreeMaxWidth {
public static class Node {
public int value;
public Node left;
public Node right;
public Node(int data) {
this.value = data;
}
}
public static int maxWidthUseMap(Node head) {
if (head == null) {
return 0;
}
Queue<Node> queue = new LinkedList<>();
queue.add(head);
// key 在 哪一层，value
HashMap<Node, Integer> levelMap = new HashMap<>();
levelMap.put(head, 1);
int curLevel = 1; // 当前你正在统计哪一层的宽度
int curLevelNodes = 0; // 当前层curLevel层，宽度目前是多少
int max = 0;
while (!queue.isEmpty()) {
Node cur = queue.poll();
int curNodeLevel = levelMap.get(cur);
if (cur.left != null) {
levelMap.put(cur.left, curNodeLevel + 1);
queue.add(cur.left);
}
if (cur.right != null) {
levelMap.put(cur.right, curNodeLevel + 1);
queue.add(cur.right);
}
if (curNodeLevel == curLevel) {
curLevelNodes++;
} else {
max = Math.max(max, curLevelNodes);
curLevel++;
curLevelNodes = 1;
}
}
max = Math.max(max, curLevelNodes);
return max;
}
public static int maxWidthNoMap(Node head) {
if (head == null) {
return 0;
}
Queue<Node> queue = new LinkedList<>();
queue.add(head);
Node curEnd = head; // 当前层，最右节点是谁
Node nextEnd = null; // 下一层，最右节点是谁
int max = 0;
int curLevelNodes = 0; // 当前层的节点数
while (!queue.isEmpty()) {
Node cur = queue.poll();
if (cur.left != null) {
queue.add(cur.left);
nextEnd = cur.left;
}
if (cur.right != null) {
queue.add(cur.right);
nextEnd = cur.right;
}
curLevelNodes++;
if (cur == curEnd) {
max = Math.max(max, curLevelNodes);
curLevelNodes = 0;
curEnd = nextEnd;
}
}
return max;
}
// for test
public static Node generateRandomBST(int maxLevel, int maxValue) {
return generate(1, maxLevel, maxValue);
}
// for test
public static Node generate(int level, int maxLevel, int maxValue) {
if (level > maxLevel || Math.random() < 0.5) {
return null;
}
Node head = new Node((int) (Math.random() * maxValue));
head.left = generate(level + 1, maxLevel, maxValue);
head.right = generate(level + 1, maxLevel, maxValue);
return head;
}
public static void main(String[] args) {
int maxLevel = 10;
int maxValue = 100;
int testTimes = 1000000;
for (int i = 0; i < testTimes; i++) {
Node head = generateRandomBST(maxLevel, maxValue);
if (maxWidthUseMap(head) != maxWidthNoMap(head)) {
System.out.println("Oops!");
}
}
System.out.println("finish!");
}
}