Leetcode 542 Matrix

题目链接

• 第一版BFS：没找到毛病通不过，也是醉了（复杂度有点高呀，小伙子）

class Solution {public:   void bfs(vector<vector<int>>&matrix,int i, int j, int &cnt){        if(matrix[i][j] == 0)return;        cnt++;        if(i > 0)bfs(matrix, i-1,j,cnt);        else if(j > 0)bfs(matrix, i,j-1,cnt);        else if(i < matrix.size() -1)bfs(matrix, i +1, j,cnt);        else if(j < matrix[0].size() -1)bfs(matrix, i, j + 1,cnt);    }    vector<vector<int>> updateMatrix(vector<vector<int>>& matrix) {        vector<vector<int>> res(matrix.size(),vector<int>(matrix[0].size(),0));        for(int i = 0; i< matrix.size(); i++){            for(int j = 0; j < matrix[0].size(); j++){                int cnt = 0;                bfs(matrix,i,j, cnt);                res[i][j] = cnt;            }        }        return res;    }};

• 第二版DP，over

class Solution {public:    vector<vector<int>> updateMatrix(vector<vector<int>>& matrix) {        vector<vector<int>> res(matrix.size(),vector<int>(matrix[0].size(),INT_MAX));        for(int i = 0; i< matrix.size(); i++){            for(int j = 0; j < matrix[0].size(); j++){                if(matrix[i][j] == 0)res[i][j]=0;                if(i > 0 && res[i-1][j] != INT_MAX)res[i][j] = min(res[i][j],res[i-1][j]+1);                if(j > 0 && res[i][j-1] != INT_MAX)res[i][j] = min(res[i][j],res[i][j-1]+1);            }        }        for(int i = matrix.size()-1; i>=0; i--){            for(int j = matrix[0].size()-1; j >=0; j--){                if(matrix[i][j] == 0)res[i][j]=0;                if(i < matrix.size()-1 && res[i+1][j]!= INT_MAX)res[i][j] = min(res[i][j],res[i+1][j]+1);                if(j < matrix[0].size()-1  && res[i][j+1] != INT_MAX )res[i][j] = min(res[i][j],res[i][j+1]+1);            }        }        return res;    }};