README_EN.md

240. Search a 2D Matrix II

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Description

Write an efficient algorithm that searches for a target value in an m x n integer matrix. The matrix has the following properties:

• Integers in each row are sorted in ascending from left to right.
• Integers in each column are sorted in ascending from top to bottom.

 

Example 1:

Input: matrix = [[1,4,7,11,15],[2,5,8,12,19],[3,6,9,16,22],[10,13,14,17,24],[18,21,23,26,30]], target = 5
Output: true

Example 2:

Input: matrix = [[1,4,7,11,15],[2,5,8,12,19],[3,6,9,16,22],[10,13,14,17,24],[18,21,23,26,30]], target = 20
Output: false

 

Constraints:

• m == matrix.length
• n == matrix[i].length
• 1 <= n, m <= 300
• -109 <= matix[i][j] <= 109
• All the integers in each row are sorted in ascending order.
• All the integers in each column are sorted in ascending order.
• -109 <= target <= 109

Solutions

Python3

class Solution:
    def searchMatrix(self, matrix: List[List[int]], target: int) -> bool:
        m, n = len(matrix), len(matrix[0])
        i, j = m - 1, 0
        while i >= 0 and j < n:
            if matrix[i][j] == target:
                return True
            if matrix[i][j] > target:
                i -= 1
            else:
                j += 1
        return False

Java

class Solution {
    public boolean searchMatrix(int[][] matrix, int target) {
        int m = matrix.length, n = matrix[0].length;
        int i = m - 1, j = 0;
        while (i >= 0 && j < n) {
            if (matrix[i][j] == target) {
                return true;
            }
            if (matrix[i][j] > target) {
                --i;
            } else {
                ++j;
            }
        }
        return false;
    }
}

TypeScript

function searchMatrix(matrix: number[][], target: number): boolean {
    let m = matrix.length, n = matrix[0].length;
    let i = m - 1, j = 0;
    while (i >= 0 && j < n) {
        let cur = matrix[i][j];
        if (cur == target) return true;
        if (cur > target) {
            --i;
        } else {
            ++j;
        }
    }
    return false;
};

C++

class Solution {
public:
    bool searchMatrix(vector<vector<int>>& matrix, int target) {
        int m = matrix.size(), n = matrix[0].size();
        int i = m - 1, j = 0;
        while (i >= 0 && j < n)
        {
            if (matrix[i][j] == target) return true;
            if (matrix[i][j] > target) --i;
            else ++j;
        }
        return false;
    }
};

Go

func searchMatrix(matrix [][]int, target int) bool {
	m, n := len(matrix), len(matrix[0])
	i, j := m-1, 0
	for i >= 0 && j < n {
		if matrix[i][j] == target {
			return true
		}
		if matrix[i][j] > target {
			i--
		} else {
			j++
		}
	}
	return false
}

C#

public class Solution {
    public bool SearchMatrix(int[][] matrix, int target) {
        int m = matrix.Length, n = matrix[0].Length;
        int i = m - 1, j = 0;
        while (i >= 0 && j < n)
        {
            if (matrix[i][j] == target)
            {
                return true;
            }
            if (matrix[i][j] > target)
            {
                --i;
            }
            else
            {
                ++j;
            }
        }
        return false;
    }
}

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