295. 数据流的中位数
中位数是有序整数列表中的中间值。如果列表的大小是偶数，则没有中间值，中位数是两个中间值的平均值。
例如 arr = [2,3,4] 的中位数是 3 。
例如 arr = [2,3] 的中位数是 (2 + 3) / 2 = 2.5 。
实现 MedianFinder 类:
MedianFinder() 初始化 MedianFinder 对象。
void addNum(int num) 将数据流中的整数 num 添加到数据结构中。
double findMedian() 返回到目前为止所有元素的中位数。与实际答案相差 10-5 以内的答案将被接受。list 存储 超时
java
class MedianFinder {
List<Integer> list = new ArrayList<>();
public MedianFinder() {
}
public void addNum(int num) {
int i = list.size();
while (i > 0) {
if (num < list.get(i-1)) {
i-=1;
} else {
break;
}
}
if (i == list.size()) {
list.add(num);
} else {
list.add(i, num);
}
}
public double findMedian() {
int l = list.size();
if (l % 2 == 1) {
return list.get(l/2);
}
return (list.get(l/2) + list.get(l/2-1)) / 2.0D;
}
}
/**
* Your MedianFinder object will be instantiated and called as such:
* MedianFinder obj = new MedianFinder();
* obj.addNum(num);
* double param_2 = obj.findMedian();
*/最大最小堆
java
class MedianFinder {
PriorityQueue<Integer> maxHeap = new PriorityQueue<Integer>((a, b) -> b-a);
PriorityQueue<Integer> minHeap = new PriorityQueue<Integer>((a, b) -> a-b);
public MedianFinder() {
}
public void addNum(int num) {
if (maxHeap.isEmpty() || num < maxHeap.peek()) {
maxHeap.offer(num);
if (minHeap.size() + 1 < maxHeap.size()){
minHeap.offer(maxHeap.poll());
}
} else {
minHeap.offer(num);
if (minHeap.size() > maxHeap.size()) {
maxHeap.offer(minHeap.poll());
}
}
}
public double findMedian() {
if (maxHeap.size() > minHeap.size()) {
return maxHeap.peek();
}
return (minHeap.peek() + maxHeap.peek()) / 2.0D;
}
}
/**
* Your MedianFinder object will be instantiated and called as such:
* MedianFinder obj = new MedianFinder();
* obj.addNum(num);
* double param_2 = obj.findMedian();
*/