程序员面试金典---20

井字游戏

思路：

朴素求解

1. 先判断横、竖、两个对角线
2. 如果前面判断无法得出结果，用函数countSpace判断是否有空格，有代表没有填满，输出Pending、否则输出Draw。

代码：

/**
 * @param {string[]} board
 * @return {string}
 */
var tictactoe = function (board) {
  if (board.length == 1 || !board[0][0]) {
    return board[0][0];
  }
  
  if (horizontal(board) || vertical(board) || 
      diagonal(board) || negativeDiagonal(board)) {
    return horizontal(board) || vertical(board) || 
           diagonal(board) || negativeDiagonal(board)
  }

  return countSpace(board) ? "Pending" : "Draw";
};

function horizontal(board) {
  for (let i = 0; i < board.length; i++) {
    let count = 1;
    let char = board[i][0];

    for (let j = 1; j < board[i].length; j++) {
      if (char == ' ' || char !== board[i][j]) {
        break;
      } else {
        count++;
      }
    }

    if (count === board.length) {
      return char;
    }
  }
}


function vertical(board) {
  for (let i = 0; i < board.length; i++) {
    let count = 1;
    let char = board[0][i];

    for (let j = 1; j < board[i].length; j++) {
      if (char == ' ' || char !== board[j][i]) {
        break;
      } else {
        count++;
      }
    }

    if (count === board.length) {
      return char;
    }
  }
}

function diagonal(board) {
  let count = 1;
  let char = board[0][0];

  for (let i = 1; i < board.length; i++) {
    if (char == ' ' || char !== board[i][i]) {
      break;
    } else {
      count++;
    }
  }

  if (count === board.length) {
    return char;
  }
}

function negativeDiagonal(board) {
  let count = 1;
  let j = board.length - 1;
  let char = board[0][j];

  for (let i = 1; i < board.length; i++) {
    if (char == ' ' || char !== board[i][j - 1]) {
      break;
    } else {
      count++;
    }
    j--;
  }
  if (count === board.length) {
    return char;
  }
}
function countSpace(board) {
  for (let i = 0; i < board.length; i++) {
    for (let j = 0; j < board[i].length; j++) {
      if (board[i][j] == ' ') {
        return true;
      }
    }
  }

  return false;
}

阶乘尾零

代码：

/**
 * @param {number} n
 * @return {number}
 */
// 除5取整的问题
var trailingZeroes = function(n) {
    let res = 0
    while(n !== 0){
        n = Math.floor(n / 5)
        res += n
    }
    return res

};