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130.被围绕的区域 题目可以转换成，从4个边界开始向内搜索字母 O，标记所有与它直接或间接相连的字母 O int m,n; void solve(vector<vector<char>>& board) { n = board.size(); if (n == 0) return; m = board[0].size(); for (int i = 0; i < n; i++) { dfs(board, i, 0); dfs(board, i, m - 1); } for (int i = 1; i < m - 1; i++) { dfs(board, 0, i); dfs(board, n - 1, i); } for (int i = 0; i < n; i++) { for (int j = 0; j < m; j++) { if (board[i][j] == 'A') { board[i][j] = 'O'; } else if (board[i][j] == 'O') { board[i][j] = 'X'; } } } } void dfs(vector<vector<char>>& board, int x, int y) { if (x < 0 || x >= n || y < 0 || y >= m || board[x][y] != 'O') { return; } board[x][y] = 'A'; dfs(board, x + 1, y); dfs(board, x - 1, y); dfs(board, x, y + 1); dfs(board, x,......