diff --git a/Solution/452. Minimum Number of Arrows to Burst Balloons/452. Minimum Number of Arrows to Burst Balloons.py b/Solution/452. Minimum Number of Arrows to Burst Balloons/452. Minimum Number of Arrows to Burst Balloons.py new file mode 100644 index 0000000..0bade91 --- /dev/null +++ b/Solution/452. Minimum Number of Arrows to Burst Balloons/452. Minimum Number of Arrows to Burst Balloons.py @@ -0,0 +1,8 @@ +class Solution: + def findMinArrowShots(self, points: List[List[int]]) -> int: + ans, last = 0, -inf + for a, b in sorted(points, key=lambda x: x[1]): + if a > last: + ans += 1 + last = b + return ans \ No newline at end of file diff --git a/Solution/452. Minimum Number of Arrows to Burst Balloons/readme.md b/Solution/452. Minimum Number of Arrows to Burst Balloons/readme.md new file mode 100644 index 0000000..a098f35 --- /dev/null +++ b/Solution/452. Minimum Number of Arrows to Burst Balloons/readme.md @@ -0,0 +1,135 @@ +--- +comments: true +difficulty: Medium +edit_url: Antim +tags: + - Greedy + - Array + - Sorting +--- + + + +# [452. Minimum Number of Arrows to Burst Balloons](https://leetcode.com/problems/minimum-number-of-arrows-to-burst-balloons) + +## Description + + + +

There are some spherical balloons taped onto a flat wall that represents the XY-plane. The balloons are represented as a 2D integer array points where points[i] = [xstart, xend] denotes a balloon whose horizontal diameter stretches between xstart and xend. You do not know the exact y-coordinates of the balloons.

+ +

Arrows can be shot up directly vertically (in the positive y-direction) from different points along the x-axis. A balloon with xstart and xend is burst by an arrow shot at x if xstart <= x <= xend. There is no limit to the number of arrows that can be shot. A shot arrow keeps traveling up infinitely, bursting any balloons in its path.

+ +

Given the array points, return the minimum number of arrows that must be shot to burst all balloons.

+ +

 

+

Example 1:

+ +
+Input: points = [[10,16],[2,8],[1,6],[7,12]]
+Output: 2
+Explanation: The balloons can be burst by 2 arrows:
+- Shoot an arrow at x = 6, bursting the balloons [2,8] and [1,6].
+- Shoot an arrow at x = 11, bursting the balloons [10,16] and [7,12].
+
+ +

Example 2:

+ +
+Input: points = [[1,2],[3,4],[5,6],[7,8]]
+Output: 4
+Explanation: One arrow needs to be shot for each balloon for a total of 4 arrows.
+
+ +

Example 3:

+ +
+Input: points = [[1,2],[2,3],[3,4],[4,5]]
+Output: 2
+Explanation: The balloons can be burst by 2 arrows:
+- Shoot an arrow at x = 2, bursting the balloons [1,2] and [2,3].
+- Shoot an arrow at x = 4, bursting the balloons [3,4] and [4,5].
+
+ +

 

+

Constraints:

+ + + + + +## Solutions + + + +### Solution 1 + + + +#### Python3 + +```python +class Solution: + def findMinArrowShots(self, points: List[List[int]]) -> int: + ans, last = 0, -inf + for a, b in sorted(points, key=lambda x: x[1]): + if a > last: + ans += 1 + last = b + return ans +``` + +#### Java + +```java +class Solution { + public int findMinArrowShots(int[][] points) { + // 直接 a[1] - b[1] 可能会溢出 + Arrays.sort(points, Comparator.comparingInt(a -> a[1])); + int ans = 0; + long last = -(1L << 60); + for (var p : points) { + int a = p[0], b = p[1]; + if (a > last) { + ++ans; + last = b; + } + } + return ans; + } +} +``` + +#### C++ + +```cpp +class Solution { +public: + int findMinArrowShots(vector>& points) { + sort(points.begin(), points.end(), [](vector& a, vector& b) { + return a[1] < b[1]; + }); + int ans = 0; + long long last = -(1LL << 60); + for (auto& p : points) { + int a = p[0], b = p[1]; + if (a > last) { + ++ans; + last = b; + } + } + return ans; + } +}; +``` + + + + + + + \ No newline at end of file