0598. Range Addition II

https://leetcode.com/problems/range-addition-ii

Description

You are given an m x n matrix M initialized with all 0's and an array of operations ops, where ops[i] = [ai, bi] means M[x][y] should be incremented by one for all 0 <= x < ai and 0 <= y < bi.

Count and return the number of maximum integers in the matrix after performing all the operations.

Example 1:

**Input:** m = 3, n = 3, ops = [[2,2],[3,3]]
**Output:** 4
**Explanation:** The maximum integer in M is 2, and there are four of it in M. So return 4.

Example 2:

**Input:** m = 3, n = 3, ops = [[2,2],[3,3],[3,3],[3,3],[2,2],[3,3],[3,3],[3,3],[2,2],[3,3],[3,3],[3,3]]
**Output:** 4

Example 3:

**Input:** m = 3, n = 3, ops = []
**Output:** 9

Constraints:

• 1 <= m, n <= 4 * 104

• 0 <= ops.length <= 104

• ops[i].length == 2

• 1 <= ai <= m

• 1 <= bi <= n

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