LeetCode 1428: Leftmost Column with at Least a One Solution

Master LeetCode problem 1428 (Leftmost Column with at Least a One), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

1428. Leftmost Column with at Least a One

Medium

Array Binary Search Matrix Interactive

Problem Explanation

Explanation

To find the leftmost column with at least a one in a binary matrix, we can start from the top-right corner and move left or down based on the value in each cell. This way, we can gradually narrow down the potential column with at least one in the matrix.

Start at the top-right corner of the matrix.
If the current cell value is 0, move down one row.
If the current cell value is 1, move left one column.
Repeat steps 2 and 3 until we reach the bottom-left corner of the matrix.

The key idea is to leverage the properties of a sorted binary matrix to optimize the search for the leftmost column with a one.

Time complexity: O(rows + columns)
Space complexity: O(1)

Solution Code

class Solution {
    public int leftMostColumnWithOne(BinaryMatrix binaryMatrix) {
        List<Integer> dimensions = binaryMatrix.dimensions();
        int rows = dimensions.get(0);
        int columns = dimensions.get(1);
        
        int currentRow = 0;
        int currentColumn = columns - 1;
        int leftmostColumn = -1;
        
        while (currentRow < rows && currentColumn >= 0) {
            if (binaryMatrix.get(currentRow, currentColumn) == 1) {
                leftmostColumn = currentColumn;
                currentColumn--;
            } else {
                currentRow++;
            }
        }
        
        return leftmostColumn;
    }
}

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