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100 lines (80 loc) · 2.19 KB
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// Source : https://leetcode.com/problems/number-of-islands/
// Author : Hao Chen
// Date : 2015-06-08
/**********************************************************************************
*
* Given a 2d grid map of '1's (land) and '0's (water), count the number of islands.
* An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically.
* You may assume all four edges of the grid are all surrounded by water.
*
* Example 1:
* 11110
* 11010
* 11000
* 00000
* Answer: 1
*
* Example 2:
* 11000
* 11000
* 00100
* 00011
* Answer: 3
*
* Credits:Special thanks to @mithmatt for adding this problem and creating all test cases.
*
**********************************************************************************/
#include <iostream>
#include <vector>
using namespace std;
void mark(vector<vector<char> >& grid, int r, int c){
if ( r<0 || r>=grid.size() ||
c<0 || c>=grid[0].size() ||
grid[r][c] != '1' ) {
return;
}
grid[r][c] = 'M';
mark(grid, r, c+1); //left
mark(grid, r, c-1); //right
mark(grid, r-1, c); //up
mark(grid, r+1, c); //down
}
int numIslands(vector<vector<char> >& grid) {
int result = 0;
for (int r=0; r<grid.size(); r++) {
for (int c=0; c<grid[r].size(); c++) {
if (grid[r][c] == '1') {
result++;
mark(grid, r, c);
}
}
}
return result;
}
void initGrid( string g[], int len, vector<vector<char> >& grid )
{
for (int i=0; i<len; i++){
grid.push_back(vector<char>(g[i].begin(), g[i].end()));
}
}
int main(void)
{
vector< vector<char> > grid;
grid.push_back( vector<char>(1, '1') );
cout << numIslands(grid) << endl;
grid.clear();
string g1[] = { "11110",
"11010",
"11000",
"00000" };
initGrid(g1, 4, grid);
cout << numIslands(grid) << endl;
grid.clear();
string g2[] = { "11000",
"11000",
"00100",
"00011" };
initGrid(g2, 4, grid);
cout << numIslands(grid) << endl;
return 0;
}