diff --git a/0286-Walls-and-Gates/cpp-0286/main.cpp b/0286-Walls-and-Gates/cpp-0286/main.cpp
index be0900d6..bf8a9a6a 100644
--- a/0286-Walls-and-Gates/cpp-0286/main.cpp
+++ b/0286-Walls-and-Gates/cpp-0286/main.cpp
@@ -1,6 +1,7 @@
 /// Source : https://leetcode.com/problems/walls-and-gates/description/
 /// Author : liuyubobobo
 /// Time   : 2018-08-25
+/// Updated: 2019-06-12
 
 #include <iostream>
 #include <vector>
@@ -15,30 +16,36 @@ using namespace std;
 class Solution {
 
 private:
-    int d[4][2] = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
-    int n, m;
+    const int d[4][2] = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
+    int m, n;
+
+    const int GATE = 0;
+    const int EMPTY = INT_MAX;
+    const int WALL = -1;
 
 public:
     void wallsAndGates(vector<vector<int>>& rooms) {
 
-        n = rooms.size();
-        if(n == 0)
+        m = rooms.size();
+        if(m == 0)
             return;
-        m = rooms[0].size();
-        for(int i = 0; i < n; i ++)
-            for(int j = 0; j < m; j ++)
-                if(rooms[i][j] == 0)
-                    bfs(rooms, i, j);
+        n = rooms[0].size();
+
+        bfs(rooms);
         return;
     }
 
 private:
-    void bfs(vector<vector<int>>& rooms, int startx, int starty){
+    void bfs(vector<vector<int>>& rooms){
 
-        vector<vector<bool>> visited(n, vector<bool>(m, false));
         queue<pair<pair<int, int>, int>> q;
-        q.push(make_pair(make_pair(startx, starty), 0));
-        visited[startx][starty] = true;
+        for(int i = 0; i < m; i ++)
+            for(int j = 0; j < n; j ++)
+                if(rooms[i][j] == GATE)
+                    q.push(make_pair(make_pair(i, j), 0));
+
+        vector<vector<bool>> visited(m, vector<bool>(n, false));
+
         while(!q.empty()){
             int curx = q.front().first.first;
             int cury = q.front().first.second;
@@ -49,19 +56,17 @@ class Solution {
             for(int i = 0; i < 4; i ++){
                 int newX = curx + d[i][0];
                 int newY = cury + d[i][1];
-                if(inArea(newX, newY) && !visited[newX][newY] && rooms[newX][newY] >= 0){
+                if(inArea(newX, newY) && !visited[newX][newY] && rooms[newX][newY] == EMPTY){
                     visited[newX][newY] = true;
-                    if(rooms[newX][newY] > step + 1){
-                        rooms[newX][newY] = step + 1;
-                        q.push(make_pair(make_pair(newX, newY), step + 1));
-                    }
+                    rooms[newX][newY] = step + 1;
+                    q.push(make_pair(make_pair(newX, newY), step + 1));
                 }
             }
         }
     }
 
     bool inArea(int x, int y){
-        return x >= 0 && x < n && y >= 0 && y < m;
+        return x >= 0 && x < m && y >= 0 && y < n;
     }
 };