# 986.Interval-List-Intersections

## 986. Interval List Intersections

## 题目地址

<https://leetcode.com/problems/interval-list-intersections/>

## 题目描述

```
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:
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.
```

## 代码

### Approach #1 Merge Intervals

Time && Space Complexity: O(M + N)

```java
class Solution {
  public int[][] intervalIntersection(int[][] A, int[][] B) {
        List<int[]> ans = new ArrayList();
    int i = 0, j = 0;

    while (i < A.length && j < B.length) {
      int lo = Math.max(A[i][0], B[j][0]);
      int hi = Math.min(A[i][1], B[j][1]);
      if (lo <= hi) {
        ans.add(new int[]{lo, hi});
      }

      // 合并小的end
      if (A[i][1] < B[j][1]) {
        i++;
      } else {
        j++;
      }
    }

    return ans.toArray(new int[ans.size()][]);
  }
}
```


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