From 9f38af3e3a61562b17530302e8d14a6a02d1835f Mon Sep 17 00:00:00 2001
From: Hang <69448559+silaslll@users.noreply.github.com>
Date: Sun, 5 Jun 2022 17:59:15 -0400
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更新了java代码，增加了一个 leftmostRightBound variable 记录最小的右边界使得代码可读性增加
加入了comment
解释了Arrays.sort(points, (x, y) -> Integer.compare(x[0], y[0])); 中不用 x[0] - y[0] 而是用Integer.compare(x[0], y[0]) 的原因
加入了时空复杂度和说明
---
 .../0452.用最少数量的箭引爆气球.md | 21 ++++++++++++++-----
 1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/problems/0452.用最少数量的箭引爆气球.md b/problems/0452.用最少数量的箭引爆气球.md
index d4bbe961..58422d4c 100644
--- a/problems/0452.用最少数量的箭引爆气球.md
+++ b/problems/0452.用最少数量的箭引爆气球.md
@@ -136,17 +136,28 @@ public:
 
 ### Java 
 ```java
+/**
+时间复杂度 : O(NlogN)  排序需要 O(NlogN) 的复杂度
+
+空间复杂度 : O(logN) java所使用的内置函数用的是快速排序需要 logN 的空间
+*/
 class Solution {
     public int findMinArrowShots(int[][] points) {
         if (points.length == 0) return 0;
-        Arrays.sort(points, (o1, o2) -> Integer.compare(o1[0], o2[0]));
-
+        //用x[0] - y[0] 会大于2147483647 造成整型溢出
+        Arrays.sort(points, (x, y) -> Integer.compare(x[0], y[0]));
+        //count = 1 因为最少需要一个箭来射击第一个气球
         int count = 1;
-        for (int i = 1; i < points.length; i++) {
-            if (points[i][0] > points[i - 1][1]) {
+        //重叠气球的最小右边界
+        int leftmostRightBound  = points[0][1];
+        //如果下一个气球的左边界大于最小右边界
+            if (points[i][0] > leftmostRightBound ) {
+                //增加一次射击
                 count++;
+                leftmostRightBound  = points[i][1];
+                //不然就更新最小右边界
             } else {
-                points[i][1] = Math.min(points[i][1],points[i - 1][1]);
+                leftmostRightBound  = Math.min(leftmostRightBound , points[i][1]);
             }
         }
         return count;