leetcode：0-1 矩阵问题

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//DFS (Time Limited)class Solution {public:    int dfs(vector<vector<int>> &matrix,int i,int j,int R,int C,bool** visited){        int res=R+C;        if (0==matrix[i][j]) return 0;        visited[i][j]=true;        if (j>0&&!visited[i][j-1]){//left            res=min(res,1+dfs(matrix,i,j-1,R,C,visited));        }        if (j<C-1&&!visited[i][j+1]){//right            res=min(res,1+dfs(matrix,i,j+1,R,C,visited));        }        if (i>0&&!visited[i-1][j]){//up            res=min(res,1+dfs(matrix,i-1,j,R,C,visited));        }        if (i<R-1&&!visited[i+1][j]){//down             res=min(res,1+dfs(matrix,i+1,j,R,C,visited));        }        visited[i][j]=false;        return res;    }    vector<vector<int>> updateMatrix(vector<vector<int>>& matrix) {        int R=matrix.size(),C=matrix[0].size();        vector<vector<int>> ret(R,vector<int>(C,0));        bool **visited=new bool *[R];        for (int i=0;i<R;i++){           visited[i]=new bool [C];           fill(visited[i],visited[i]+C,false);        }        for (int i=0;i<R;i++){            for (int j=0;j<C;j++){                ret[i][j]=dfs(matrix,i,j,R,C,visited);            }        }        delete [] visited;        return ret;    }};

//BFSclass Solution {public:    //BFS 只进入合法节点    vector<vector<int>> updateMatrix(vector<vector<int>>& matrix) {        int R=matrix.size(),C=matrix[0].size();        queue<pair<int,int>> q;        vector<pair<int,int>> adjust={{0,-1},{0,1},{-1,0},{1,0}};        for (int i=0;i<R;i++){            for (int j=0;j<C;j++){                if (0==matrix[i][j]) q.push({i,j});                else matrix[i][j]=INT_MAX;            }        }        while(!q.empty()){            pair<int,int> coordinate=q.front();            q.pop();            int i=coordinate.first,j=coordinate.second;            for (auto d:adjust){                auto x=i+d.first,y=j+d.second;                if(x>=0 && x<R && y>=0 && y<C){                    if (matrix[x][y]>=matrix[i][j]+1){//careful                        matrix[x][y]=1+matrix[i][j];                        q.push({x,y});                    }                 }            }        }        return matrix;    }};

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