【剑指offer第十四天】搜索算法与回溯

class Solution {
    public boolean exist(char[][] board, String word) {
        char []tmp = word.toCharArray();
        int r = board.length;
        int c = board[0].length;
        for(int i = 0;i < r;i++){
            for(int j = 0;j < c;j++){
                if(backtrack(board,tmp,i,j,0)) return true;
            }
        }
        return false;
    }
    public boolean backtrack(char[][] board,char[] word,int i,int j,int k){
        if(i < 0||i >= board.length||j < 0||j >= board[0].length||board[i][j]!=word[k]){
            return false;
        }
        if(k == word.length-1){
            return true;
        }
        board[i][j] = '\0';
        boolean res = backtrack(board,word,i+1,j,k+1)||
                      backtrack(board,word,i,j+1,k+1)||
                      backtrack(board,word,i,j-1,k+1)||
                      backtrack(board,word,i-1,j,k+1);
        board[i][j] = word[k];
        return res;
    }
}

class Solution {
    public int movingCount(int m, int n, int k) {
        boolean[][] visit = new boolean[m][n];
        return dfs(visit,m,n,k,0,0);
    }
    public int dfs(boolean [][]visit,int m,int n,int k,int i,int j){
        if(i >= m||j >= n||visit[i][j]||sum(i)+sum(j)>k){
            return 0;
        }
        visit[i][j] = true;
        return 1 + dfs(visit,m,n,k,i+1,j) + dfs(visit,m,n,k,i,j+1);
    }
    public int sum(int k){
        int res = 0;
        while(k != 0){
            res += k%10;
            k /= 10;
        }
        return res;
    }
}