How do I convert a chessboard letter to a number in this problem?

Map letters 'a' to 'h' to numbers 1 through 8, which allows you to compute sums for parity checking.

Why does adding row and column indices determine the square color?

Because the chessboard alternates colors, the sum of column and row indices being even or odd directly maps to black or white squares.

Can this approach handle multiple coordinates at once?

Yes, convert each coordinate individually and apply the sum parity logic to compute a boolean array of results.

What pattern does this problem illustrate?

This is a Math plus String pattern where string parsing is combined with numeric calculations to evaluate parity.

What are common mistakes when implementing this solution?

Reversing the color logic, off-by-one errors in letter-to-number conversion, or summing indices incorrectly.

#1812

Easy

auto_awesome数学·string

LeetCode 题解工作台

判断国际象棋棋盘中一个格子的颜色

给你一个坐标 coordinates ，它是一个字符串，表示国际象棋棋盘中一个格子的坐标。下图是国际象棋棋盘示意图。如果所给格子的颜色是白色，请你返回 true ，如果是黑色，请返回 false 。给定坐标一定代表国际象棋棋盘上一个存在的格子。坐标第一个字符是字母，第二个字符是数字。示例 1：…

数学字符串

题目描述

给你一个坐标 coordinates ，它是一个字符串，表示国际象棋棋盘中一个格子的坐标。下图是国际象棋棋盘示意图。

如果所给格子的颜色是白色，请你返回 true，如果是黑色，请返回 false 。

给定坐标一定代表国际象棋棋盘上一个存在的格子。坐标第一个字符是字母，第二个字符是数字。

示例 1：

输入：coordinates = "a1"
输出：false
解释：如上图棋盘所示，"a1" 坐标的格子是黑色的，所以返回 false 。

示例 2：

输入：coordinates = "h3"
输出：true
解释：如上图棋盘所示，"h3" 坐标的格子是白色的，所以返回 true 。

示例 3：

输入：coordinates = "c7"
输出：false

提示：

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

lightbulb

解题思路

方法一：找规律

观察棋盘我们发现，颜色相同的两个格子 $(x_1, y_1)$ 和 $(x_2, y_2)$ 满足 $x_1 + y_1$ 和 $x_2 + y_2$ 均为奇数或偶数。

因此，我们可以根据 $\textit{coordinates}$ 获取对应的坐标 $(x, y)$ ，如果 $x + y$ 为奇数，则格子为白色，返回 $\textit{true}$ ，否则返回 $\textit{false}$ 。

时间复杂度 $O(1)$ ，空间复杂度 $O(1)$ 。

1

2

3

4

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

speed

复杂度分析

指标	值
时间	complexity is O(1) because coordinate conversion and arithmetic are constant operations. Space complexity is O(1) as only a few integer variables are needed.
空间	Depends on the final approach

psychology

面试官常问的追问

外企场景

question_mark
The candidate understands converting characters to numeric indices for computation.
question_mark
They identify that parity determines the chessboard color pattern.
question_mark
They correctly handle the mapping of letters 'a' to 'h' to numerical values without off-by-one errors.

warning

常见陷阱

外企场景

error
Misinterpreting the color mapping by reversing black and white parity.
error
Off-by-one errors when converting letters to numbers ('a' vs 1).
error
Ignoring that the sum of indices, not individual indices, determines the color.

swap_horiz

进阶变体

外企场景

arrow_right_alt
Determine color for a rectangular chessboard of arbitrary size using the same parity approach.
arrow_right_alt
Return the color as a string 'white' or 'black' instead of a boolean.
arrow_right_alt
Given multiple coordinates, compute an array of boolean results for all squares efficiently.

help

常见问题

外企场景

继续练习

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