0200-number-of-islands.ts

//BFS way to solve this
constbfs=(grid,r,c)=>{
const[ROWS,COLS]=[grid.length,grid[0].length];

constdirections=[
[-1,0],
[1,0],
[0,-1],
[0,1],
];

letqueue=[[r,c]];

//marks as visited
grid[r][c]='0';

while(queue.length>0){
//dequeues the first element(current)
let[cr,cc]=queue.shift();

directions.forEach(([dr,dc])=>{
let[nr,nc]=[cr+dr,cc+dc];
if(
!(
nr<0||
nc<0||
nr>=ROWS||
nc>=COLS||
grid[nr][nc]==='0'
)
){
queue.push([nr,nc]);
grid[nr][nc]='0';
}
});
}
};

functionnumIslands(grid: string[][]): number{
const[ROWS,COLS]=[grid.length,grid[0].length];

letislands=0;

for(leti=0;i<ROWS;i++){
for(letj=0;j<COLS;j++){
if(grid[i][j]==='1'){
bfs(grid,i,j);
islands++;
}
}
}

returnislands;
}