LeetCode-in-All

74. Search a 2D Matrix

Medium

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

• Integers in each row are sorted from left to right.
• The first integer of each row is greater than the last integer of the previous row.

Example 1:

Input: matrix = [[1,3,5,7],[10,11,16,20],[23,30,34,60]], target = 3

Output: true

Example 2:

Input: matrix = [[1,3,5,7],[10,11,16,20],[23,30,34,60]], target = 13

Output: false

Constraints:

• m == matrix.length
• n == matrix[i].length
• 1 <= m, n <= 100
• -104 <= matrix[i][j], target <= 104

Solution

function searchMatrix(matrix: number[][], target: number): boolean {
    const [m, n] = [matrix.length, matrix[0].length]
    let [l, r] = [0, m * n - 1]
    while (l <= r) {
        const mid = Math.floor((l + r) / 2)
        const row = Math.floor(mid / n)
        const col = mid % n
        const el = matrix[row][col]
        if (el === target) return true
        if (el < target) {
            l = mid + 1
        } else {
            r = mid - 1
        }
    }
    return false
}

export { searchMatrix }

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