leetcode-419.棋盘上的战舰

一.题目描述

二.第一次代码提交

class Solution {
public:
    int countBattleships(vector<vector<char>>& board) {
        int m = board.size(); //列数
        int n = board[0].size(); //行数
        int count = 0;

        for (int i = 0; i < m; i++) { //先遍历列，从左到右，i是列的游标
            for (int j = 0; j < n; j++) { //再遍历行，从上到下，j是行的游标
                if ((board[i][j] == 'X') && (i == 0 || board[i - 1][j] == '.') && (j == 0 || board[i][j - 1] == '.')) { //先左后上
                    count++;
                }
            }
        }

        return count;
    }
};

三.第二次代码提交

class Solution {
public:
    int countBattleships(vector<vector<char>>& board) {
        int m = board.size();
        int n = board[0].size();
        int count = 0;

        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                if (board[i][j] == 'X') {
                    board[i][j] = '.';
                    for(int k=i+1; k<m && board[k][j] == 'X' ;k++){ board[k][j] = '.'; }
                    for(int k=j+1; k<n && board[i][k] == 'X' ;k++){ board[i][k] = '.'; }
                    count++;
                }
            }
        }
        
        return count;
    }
};