Problem

You are given coordinates, a string that represents the coordinates of a square of the chessboard. Below is a chessboard for your reference.

Return true if the square is white, andfalse if the square is black.

The coordinate will always represent a valid chessboard square. The coordinate will always have the letter first, and the number second.

Examples

Example 1

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Input: coordinates = "a1"
Output: false
Explanation: From the chessboard above, the square with coordinates "a1" is black, so return false.

Example 2

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Input: coordinates = "h3"
Output: true
Explanation: From the chessboard above, the square with coordinates "h3" is white, so return true.

Example 3

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Input: coordinates = "c7"
Output: false

Constraints

  • coordinates.length == 2
  • 'a' <= coordinates[0] <= 'h'
  • '1' <= coordinates[1] <= '8'

Solution

Method 1 – Parity Check

Intuition

On a chessboard, the color of a square alternates every cell. The bottom-left square (‘a1’) is black. The color of a square is determined by the sum of its row and column indices: if the sum is even, it’s black; if odd, it’s white.

Approach

  1. Convert the column letter to a number (e.g., ‘a’ to 1, ‘b’ to 2, …, ‘h’ to 8).
  2. Convert the row character to an integer.
  3. If the sum of the column and row is even, return false (black); if odd, return true (white).

Code

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class Solution {
public:
    bool squareIsWhite(string coordinates) {
        int col = coordinates[0] - 'a' + 1;
        int row = coordinates[1] - '0';
        return (col + row) % 2 == 1;
    }
};
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func squareIsWhite(coordinates string) bool {
    col := int(coordinates[0]-'a') + 1
    row := int(coordinates[1]-'0')
    return (col+row)%2 == 1
}
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class Solution {
    public boolean squareIsWhite(String coordinates) {
        int col = coordinates.charAt(0) - 'a' + 1;
        int row = coordinates.charAt(1) - '0';
        return (col + row) % 2 == 1;
    }
}
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class Solution {
    fun squareIsWhite(coordinates: String): Boolean {
        val col = coordinates[0] - 'a' + 1
        val row = coordinates[1] - '0'
        return (col + row) % 2 == 1
    }
}
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class Solution:
    def squareIsWhite(self, coordinates: str) -> bool:
        col = ord(coordinates[0]) - ord('a') + 1
        row = int(coordinates[1])
        return (col + row) % 2 == 1
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impl Solution {
    pub fn square_is_white(coordinates: String) -> bool {
        let bytes = coordinates.as_bytes();
        let col = (bytes[0] - b'a' + 1) as i32;
        let row = (bytes[1] - b'0') as i32;
        (col + row) % 2 == 1
    }
}
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class Solution {
    squareIsWhite(coordinates: string): boolean {
        const col = coordinates.charCodeAt(0) - 'a'.charCodeAt(0) + 1;
        const row = Number(coordinates[1]);
        return (col + row) % 2 === 1;
    }
}

Complexity

  • ⏰ Time complexity: O(1), as all operations are constant time.
  • 🧺 Space complexity: O(1), as no extra space is used.