598. Range Addition II

Description

Given an m n matrix *M initialized with all 0's and several update operations.

Operations are represented by a 2D array, and each operation is represented by an array with two positive integers a and b, which means M[i][j] should be added by one for all 0 <= i < a and 0 <= j < b.

You need to count and return the number of maximum integers in the matrix after performing all the operations.

Example 1:

Input:
m = 3, n = 3
operations = [[2,2],[3,3]]
Output: 4
Explanation:
Initially, M = 
[[0, 0, 0],
 [0, 0, 0],
 [0, 0, 0]]

After performing [2,2], M = 
[[1, 1, 0],
 [1, 1, 0],
 [0, 0, 0]]

After performing [3,3], M = 
[[2, 2, 1],
 [2, 2, 1],
 [1, 1, 1]]

So the maximum integer in M is 2, and there are four of it in M. So return 4.

Note:

1. The range of m and n is [1,40000].
2. The range of a is [1,m], and the range of b is [1,n].
3. The range of operations size won't exceed 10,000.

Solution

/**
 * @param {number} m
 * @param {number} n
 * @param {number[][]} ops
 * @return {number}
 */
var maxCount = function(m, n, ops) {
    "use strict";
    if (ops.length === 0) {
        return m*n;
    }
    // Find the intersection of all the operations performing on the matrix
    let intersectX = ops[0][0];
    let intersectY = ops[0][1];
    for (let i = 1; i < ops.length; i++) {
        if (intersectX > ops[i][0]) {
            intersectX = ops[i][0];
        }
        if (intersectY > ops[i][1]) {
            intersectY = ops[i][1];
        }
    }
    return intersectX*intersectY;
};