1812. Determine Color of a Chessboard Square

Description

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, and false 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.

 

Example 1:

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

Example 2:

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

Example 3:

Input: coordinates = "c7"
Output: false

 

Constraints:

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

Solutions

Solution 1: Pattern Recognition

Observing the chessboard, we find that two squares $(x_1, y_1)$ and $(x_2, y_2)$ with the same color satisfy that both $x_1 + y_1$ and $x_2 + y_2$ are either odd or even.

Therefore, we can get the corresponding coordinates $(x, y)$ from $\textit{coordinates}$. If $x + y$ is odd, the square is white, and we return $\textit{true}$; otherwise, we return $\textit{false}$.

The time complexity is $O(1)$, and the space complexity is $O(1)$.

Python3JavaC++GoTypeScriptRustJavaScriptC

class Solution:
    def squareIsWhite(self, coordinates: str) -> bool:
        return (ord(coordinates[0]) + ord(coordinates[1])) % 2 == 1

class Solution {
    public boolean squareIsWhite(String coordinates) {
        return (coordinates.charAt(0) + coordinates.charAt(1)) % 2 == 1;
    }
}

class Solution {
public:
    bool squareIsWhite(string coordinates) {
        return (coordinates[0] + coordinates[1]) % 2;
    }
};

func squareIsWhite(coordinates string) bool {
    return (coordinates[0]+coordinates[1])%2 == 1
}

function squareIsWhite(coordinates: string): boolean {
    return ((coordinates.charCodeAt(0) + coordinates.charCodeAt(1)) & 1) === 1;
}

impl Solution {
    pub fn square_is_white(coordinates: String) -> bool {
        let s = coordinates.as_bytes();
        ((s[0] + s[1]) & 1) == 1
    }
}

/**
 * @param {string} coordinates
 * @return {boolean}
 */
var squareIsWhite = function (coordinates) {
    return (coordinates[0].charCodeAt() + coordinates[1].charCodeAt()) % 2 == 1;
};

bool squareIsWhite(char* coordinates) {
    return (coordinates[0] + coordinates[1]) & 1;
}

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