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n-queens.js
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n-queens.js
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// The n-queens puzzle is the problem of placing n queens on an n×n chessboard such that no two queens attack each other.
//
//
//
// Given an integer n, return all distinct solutions to the n-queens puzzle.
//
// Each solution contains a distinct board configuration of the n-queens' placement, where 'Q' and '.' both indicate a queen and an empty space respectively.
//
// Example:
//
//
// Input: 4
// Output: [
// [".Q..", // Solution 1
// "...Q",
// "Q...",
// "..Q."],
//
// ["..Q.", // Solution 2
// "Q...",
// "...Q",
// ".Q.."]
// ]
// Explanation: There exist two distinct solutions to the 4-queens puzzle as shown above.
//
//
/**
* @param {number} n
* @return {string[][]}
*/
var solveNQueens = function(n) {
var result = [];
var current = new Array(n);
var isOk = function(deep, pos) {
for (var i = 0;i < deep;++i) {
if (current[i] === pos ||
Math.abs(deep - i) === Math.abs(pos - current[i])) {
return false;
}
}
return true;
};
var place = function(deep) {
if (deep === n) {
var temp = [];
for (var i = 0;i < n;++i) {
var str = new Array(n);
for (var j = 0;j < n;++j) {
str[j] = (current[i] === j ? 'Q' : '.');
}
temp.push(str.join(''));
}
result.push(temp);
return ;
}
for (var i = 0;i < n;++i) {
if (isOk(deep, i)) {
current[deep] = i;
place(deep + 1);
}
}
};
place(0);
return result;
};