Question 1 - Finding the number of islands

const input = [
	["1","1","0","0","0"], 
	["1","1","0","0","0"], 
	["0","0","1","0","0"], 
	["0","0","0","1","1"]
]

// output: 3

  
const dfs = (graph, x, y) => {  
  
    if(  
        x < 0  
        || graph.length <= x  
        || y < 0  
        || graph[x].length <= y  
        || graph[x][y] === '0'  
    ){  
        return false;  
    }  
  
    graph[x][y] = '0';  
    dfs(graph,x-1, y); //top  
    dfs(graph,x+1, y); //bottom  
    dfs(graph,x, y-1); //left  
    dfs(graph,x, y+1); //right  
}  
  
function solution(graph){  
    let result = 0;  
  
    if(graph.length === 0 || !graph){  
        return result;  
    }  
  
    for(let x = 0; x < graph.length; x++){  
        for(let y = 0; y < graph[x].length; y++){  
            if(graph[x][y] === '1'){  
                result += 1;  
                dfs(graph, x, y);  
            }  
  
        }  
    }  
  
    return result;  
}

function dfs(grid, x, y){  
    const map = [  
        [-1,0], // top  
        [1, 0], //bottom  
        [0, -1], //left  
        [0, 1] //right  
    ]  
    const stack = [[x,y]];  
  
    while(stack.length > 0){  
        const [x, y] = stack.pop();  
  
        if(  
            x < 0 ||  
            x >= grid.length ||  
            y < 0 ||  
            y >= grid[x].length ||  
            grid[x][y] === '0'  
        ){  
            continue;  
        }  
        grid[x][y] = '0';  
        for(const [mx, my] of map){  
            const newX = x+mx;  
            const newY = y+my;  
            stack.push([newX, newY]);  
        }  
    }  
  
  
}  
  
function solution(graph){  
    let result = 0;  
  
    if(graph.length === 0 || !graph){  
        return result;  
    }  
  
    for(let x = 0; x < graph.length; x++){  
        for(let y = 0; y < graph[x].length; y++){  
            if(graph[x][y] === '1'){  
                result += 1;  
                dfs(graph, x, y);  
            }  
  
        }  
    }  
  
    return result;  
}