如果知道1的位置，则找出被1包围的零的数量

Question

I am working on one programming challenge in which I have to find number of zeros surrounded by ones.

I have given:
Number of row and columns r and c
Number of positions of ones n
n positions ij where i is index of row and j is index of column

For example if I have

011110
011
011
001110
000000

then I return 6 .
There are 3 test input sets. In the first two sets r, c <= 1000 . I managed to pass the first two sets by using DFS to cout number of zeros which are not surrounded by ones (starting from borders). Hence number of zeros z = r * c - k - n where k is number of zeros which are not surrounded by ones.

But in the third case r, c <= 10^18 which doesn't even fit to memory if I create two dimensional vector on beginning. I also noticed that n is relative small in all sets ( n <= 10^6 ).

My question is how to solve this problem for all test sets?

Answer 1

Counting Rooms While Knowing Where Walls Are here you can find an result of counting the rooms wich are surrounded by walls (in your case "1") you have to change the code, that it counts the number of "0"s. But the idea is the same. Making it via bfs or dfs.