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website/content/ChapterFour/0986.Interval-List-Intersections.md

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+# [986. Interval List Intersections](https://leetcode.com/problems/interval-list-intersections/)
+
+## 题目
+
+Given two lists of closed intervals, each list of intervals is pairwise disjoint and in sorted order.
+
+Return the intersection of these two interval lists.
+
+(Formally, a closed interval [a, b] (with a <= b) denotes the set of real numbers x with a <= x <= b.  The intersection of two closed intervals is a set of real numbers that is either empty, or can be represented as a closed interval.  For example, the intersection of [1, 3] and [2, 4] is [2, 3].)
+
+
+
+
+**Example 1**:
+
+![](https://assets.leetcode.com/uploads/2019/01/30/interval1.png)
+
+```
+Input: A = [[0,2],[5,10],[13,23],[24,25]], B = [[1,5],[8,12],[15,24],[25,26]]
+Output: [[1,2],[5,5],[8,10],[15,23],[24,24],[25,25]]
+Reminder: The inputs and the desired output are lists of Interval objects, and not arrays or lists.
+```
+
+**Note**:  
+
+- 0 <= A.length < 1000
+- 0 <= B.length < 1000
+- 0 <= A[i].start, A[i].end, B[i].start, B[i].end < 10^9
+
+**Note**: input types have been changed on April 15, 2019. Please reset to default code definition to get new method signature.
+
+## 题目大意
+
+这道题考察的是滑动窗口的问题。
+
+给出 2 个数组 A 和数组 B。要求求出这 2 个数组的交集数组。题意见图。
+
+## 解题思路
+
+交集的左边界应该为，`start := max(A[i].Start, B[j].Start)`，右边界为，`end := min(A[i].End, B[j].End)`，如果 `start <= end`，那么这个就是一个满足条件的交集，放入最终数组中。如果 `A[i].End <= B[j].End`，代表 B 数组范围比 A 数组大，A 的游标右移。如果 `A[i].End > B[j].End`，代表 A 数组范围比 B 数组大，B 的游标右移。
+
+
+## 代码
+
+```go
+
+package leetcode
+
+/**
+ * Definition for an interval.
+ * type Interval struct {
+ *	   Start int
+ *	   End   int
+ * }
+ */
+func intervalIntersection(A []Interval, B []Interval) []Interval {
+	res := []Interval{}
+	for i, j := 0, 0; i < len(A) && j < len(B); {
+		start := max(A[i].Start, B[j].Start)
+		end := min(A[i].End, B[j].End)
+		if start <= end {
+			res = append(res, Interval{Start: start, End: end})
+		}
+		if A[i].End <= B[j].End {
+			i++
+		} else {
+			j++
+		}
+	}
+	return res
+}
+
+```