1 class Solution
2 {
3 private:
4 vector<pair<int,int>> graphA,graphB;
5 int colSize;
6 int mark;
7 const int xList[4] {1,0,0,-1};
8 const int yList[4] {0,1,-1,0};
9 public:
10 bool isValid(int x,int y)
11 {
12 return (x<colSize && y<colSize && x>=0 && y >= 0);
13 }
14 void floodFill(vector<vector<int>>& A,int x,int y)
15 {
16 A[x][y] = mark;
17 if(mark == 2)
18 {
19 graphA.push_back({x,y});
20 }
21 else
22 {
23 graphB.push_back({x,y});
24 }
25 for(int i = 0;i < 4;i ++)
26 {
27 int newX = x+xList[i];
28 int newY = y+yList[i];
29 if(isValid(newX,newY) && A[newX][newY] == 1)
30 {
31 floodFill(A,newX,newY);
32 }
33 }
34 }
35 int shortestBridge(vector<vector<int>>& A)
36 {
37 colSize = A.size();
38 mark = 2;
39 for(int i = 0;i < A.size();i ++)
40 {
41 for(int j = 0;j < A[i].size();j ++)
42 {
43 if(A[i][j] == 1)
44 {
45 floodFill(A,i,j);
46 mark ++;
47 }
48 }
49 }
50
51 int result = 3939;
52 for(auto p1:graphA)
53 {
54 for(auto p2:graphB)
55 {
56 if(abs(p1.first-p2.first)+abs(p1.second-p2.second) < result)
57 {
58 result = abs(p1.first-p2.first)+abs(p1.second-p2.second);
59 }
60 }
61 }
62 return result-1;
63 }
64 };
