Today is Saturday, I gonna review the tasks I've done this week, and finish today's leetcode's May LeetCoding Challenge with cpp.

LeetCode Review

Find and Replace Pattern

too easy to review

Binary Tree Level Order Traversal

too easy to review

Longest String Chain

won't review

Find Duplicate File in System

won't review

Minimum Moves to Equal Array Elements II

class Solution {
public:
  int minMoves2(vector<int>& nums) {
    int answer = 0;
    sort(nums.begin(), nums.end());
    int target = nums[nums.size() / 2];
    for(auto i : nums) answer += abs(i - target);
    return answer;
  }
};

May LeetCoding Challenge 22

Description

N-Queens

The n-queens puzzle is the problem of placing n queens on an n x 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 1:

Input: n = 4
Output: [[".Q..","...Q","Q...","..Q."],["..Q.","Q...","...Q",".Q.."]]
Explanation: There exist two distinct solutions to the 4-queens puzzle as shown above

Example 2:

Input: n = 1
Output: [["Q"]]
 
Constraints:

	
1 <= n <= 9

Solution
int rows[9];
bool check(int row, int col) {
  for(int i = 0; i < row; ++i) {
    if(abs(i - row) == abs(rows[i] - col) || col == rows[i]) return false;
  }
  return true;
}
class Solution {
  vector<vector<string>> answer;

  void addResult(int n) {
    vector<string> result;
    for(int i = 0; i < n; ++i) {
      string row(n, '.');
      row[rows[i]] = 'Q';
      result.emplace_back(row);
    }
    answer.emplace_back(result);
  }

  void solve(int cur, int n) {
    if(cur == n) {
      addResult(n);
      return;
    }
    for(int i = 0; i < n; ++i) {
      if(check(cur, i)) {
        rows[cur] = i;
        solve(cur + 1, n);
      }
    }
  }
public:
  vector<vector<string>> solveNQueens(int n) {
    solve(0, n);
    return move(answer);
  }
};