01-matrix.cpp

// https://leetcode.com/problems/01-matrix/

class Solution {
public:
    vector<vector<int>> updateMatrix(vector<vector<int>>& mat) {
        int m = mat.size();
        int n = mat[0].size();
        for(int i = 0; i<m; i++){
            for(int j = 0; j<n; j++){
                if(mat[i][j] == 0) continue;
                mat[i][j] = 100000001;
                if(i > 0) mat[i][j] = min(mat[i][j], mat[i - 1][j] + 1);
                if(j > 0) mat[i][j] = min(mat[i][j], mat[i][j - 1] + 1);
            }
        }
        for(int i = m - 1; i >= 0; i--){
            for(int j = n - 1; j >= 0; j--){
                if(mat[i][j] == 0) continue;
                if(i < m - 1) mat[i][j] = min(mat[i][j], mat[i + 1][j] + 1);
                if(j < n - 1) mat[i][j] = min(mat[i][j], mat[i][j + 1] + 1);
            }
        }
        return mat;
    }
};