LeetCode-in-All

74. Search a 2D Matrix

Medium

Write an efficient algorithm that searches for a value target in an m x n integer matrix 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

class Solution {
  bool searchMatrix(List<List<int>> matrix, int target) {
    int endRow = matrix.length;
    int endCol = matrix[0].length;
    int targetRow = 0;
    bool result = false;

    // Find the target row where target might be located
    for (int i = 0; i < endRow; i++) {
      if (matrix[i][endCol - 1] >= target) {
        targetRow = i;
        break;
      }
    }

    // Search for the target in the identified row
    for (int i = 0; i < endCol; i++) {
      if (matrix[targetRow][i] == target) {
        result = true;
        break;
      }
    }

    return result;
  }
}

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