leetcode——79.单词搜索

这道题自己完成的，不难。

回溯。

public boolean exist(char[][] board, String word) {
        int m = board.length;
        int n = board[0].length;
        int wordLength = word.length();
        if(word.length()>m*n){
            return false;
        }
        boolean[][] b = new boolean[m][n];
        for(int i = 0;i<m;i++){
            for(int j = 0;j<n;j++){
                if(board[i][j] == word.charAt(0)){
                    b[i][j] = true;
                    if(find(board,b,word,i,j,1,m,n,wordLength)){
                        return true;
                    }
                    b[i][j] = false;
                }
            }
        }
        return false;
    }

    private boolean find(char[][] board, boolean[][] b, String word, int i, int j, int k, int m, int n, int wordLength) {
        if(k == wordLength){
            return true;
        }
        if(i+1<m){
            if(!b[i+1][j] && board[i+1][j] == word.charAt(k)){
                b[i+1][j] = true;
                if(find(board, b, word, i+1, j, k+1, m, n, wordLength)){
                    return true;
                }
                b[i+1][j] = false;
            }
        }
        if(i-1>=0){
            if(!b[i-1][j] && board[i-1][j] == word.charAt(k)){
                b[i-1][j] = true;
                if(find(board, b, word, i-1, j, k+1, m, n, wordLength)){
                    return true;
                }
                b[i-1][j] = false;
            }
        }
        if(j+1<n){
            if(!b[i][j+1] && board[i][j+1] == word.charAt(k)){
                b[i][j+1] = true;
                if(find(board, b, word, i, j+1, k+1, m, n, wordLength)){
                    return true;
                }
                b[i][j+1] = false;
            }
        }
        if(j-1>=0){
            if(!b[i][j-1] && board[i][j-1] == word.charAt(k)){
                b[i][j-1] = true;
                if(find(board, b, word, i, j-1, k+1, m, n, wordLength)){
                    return true;
                }
                b[i][j-1] = false;
            }
        }
        return false;
    }

待优化。

 ——2020.6.30