2679. Sum in a Matrix

Description

You are given a 0-indexed 2D integer array nums. Initially, your score is 0. Perform the following operations until the matrix becomes empty:

  1. From each row in the matrix, select the largest number and remove it. In the case of a tie, it does not matter which number is chosen.
  2. Identify the highest number amongst all those removed in step 1. Add that number to your score.

Return the final score.

 

Example 1:

Input: nums = [[7,2,1],[6,4,2],[6,5,3],[3,2,1]]
Output: 15
Explanation: In the first operation, we remove 7, 6, 6, and 3. We then add 7 to our score. Next, we remove 2, 4, 5, and 2. We add 5 to our score. Lastly, we remove 1, 2, 3, and 1. We add 3 to our score. Thus, our final score is 7 + 5 + 3 = 15.

Example 2:

Input: nums = [[1]]
Output: 1
Explanation: We remove 1 and add it to the answer. We return 1.

 

Constraints:

  • 1 <= nums.length <= 300
  • 1 <= nums[i].length <= 500
  • 0 <= nums[i][j] <= 103

Solutions

Solution 1

Python Code
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class Solution:
    def matrixSum(self, nums: List[List[int]]) -> int:
        for row in nums:
            row.sort()
        return sum(map(max, zip(*nums)))

Java Code
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class Solution {
    public int matrixSum(int[][] nums) {
        for (var row : nums) {
            Arrays.sort(row);
        }
        int ans = 0;
        for (int j = 0; j < nums[0].length; ++j) {
            int mx = 0;
            for (var row : nums) {
                mx = Math.max(mx, row[j]);
            }
            ans += mx;
        }
        return ans;
    }
}

C++ Code
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class Solution {
public:
    int matrixSum(vector<vector<int>>& nums) {
        for (auto& row : nums) {
            sort(row.begin(), row.end());
        }
        int ans = 0;
        for (int j = 0; j < nums[0].size(); ++j) {
            int mx = 0;
            for (auto& row : nums) {
                mx = max(mx, row[j]);
            }
            ans += mx;
        }
        return ans;
    }
};

Go Code
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func matrixSum(nums [][]int) (ans int) {
	for _, row := range nums {
		sort.Ints(row)
	}
	for i := 0; i < len(nums[0]); i++ {
		mx := 0
		for _, row := range nums {
			mx = max(mx, row[i])
		}
		ans += mx
	}
	return
}

TypeScript Code
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function matrixSum(nums: number[][]): number {
    for (const row of nums) {
        row.sort((a, b) => a - b);
    }
    let ans = 0;
    for (let j = 0; j < nums[0].length; ++j) {
        let mx = 0;
        for (const row of nums) {
            mx = Math.max(mx, row[j]);
        }
        ans += mx;
    }
    return ans;
}

Rust Code
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impl Solution {
    pub fn matrix_sum(nums: Vec<Vec<i32>>) -> i32 {
        let mut nums = nums;
        for row in nums.iter_mut() {
            row.sort();
        }
        let transposed: Vec<Vec<i32>> = (0..nums[0].len())
            .map(|i| {
                nums.iter()
                    .map(|row| row[i])
                    .collect()
            })
            .collect();

        transposed
            .iter()
            .map(|row| row.iter().max().unwrap())
            .sum()
    }
}

Solution 2

Rust Code
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impl Solution {
    pub fn matrix_sum(nums: Vec<Vec<i32>>) -> i32 {
        let mut nums = nums.clone();
        for row in nums.iter_mut() {
            row.sort();
        }

        let mut ans = 0;
        for j in 0..nums[0].len() {
            let mut mx = 0;
            for row in &nums {
                mx = mx.max(row[j]);
            }
            ans += mx;
        }

        ans
    }
}