LeetCode高频面试60天打卡日记Day15

Day15 岛屿的最大面积

class Solution {
    
    
    public int maxAreaOfIsland(int[][] grid) {
    
    
        int maxArea = 0;
        for(int i=0;i<grid.length;i++){
    
    
            for(int j=0;j<grid[i].length;j++){
    
    
                if(grid[i][j]==1){
    
    
                    maxArea = Math.max(maxArea,dfs(i,j,grid));   
                }
            }
        }
        return maxArea;
    }
    //递归遍历寻找最大连续1的个数（岛屿面积）
    public int dfs(int i,int j,int[][] grid){
    
    
        if(i<0 || j<0 || i>=grid.length || j>=grid[i].length || grid[i][j]==0){
    
    
            return 0;
        }
        grid[i][j]=0;//把当前[i][j]置为0  防止回溯遍历出现栈溢出
        int num = 1;
        num += dfs(i-1,j,grid);
        num += dfs(i+1,j,grid);
        num += dfs(i,j-1,grid);
        num += dfs(i,j+1,grid);
        return num;
    }
}

//采用栈的方式   
class Solution {
    
    

    public int maxAreaOfIsland(int[][] grid) {
    
    
        Deque<int[]> stack = new LinkedList<>();

        int[][] moveIndexArray = {
    
    {
    
    -1, 0}, {
    
    1, 0}, {
    
    0, -1}, {
    
    0, 1}};
        int maxArea = 0;
        for (int i = 0; i < grid.length; i++) {
    
    
            for (int j = 0; j < grid[i].length; j++) {
    
    
                stack.add(new int[]{
    
    i, j});
                //计算最大面积
                int currMaxArea = 0;
                while (!stack.isEmpty()) {
    
    
                    int[] pop = stack.pop();
                    int currI = pop[0];
                    int currJ = pop[1];
                    if (currI < 0 || currI >= grid.length || currJ < 0 || currJ >= grid[0].length || grid[currI][currJ] == 0) {
    
    
                        continue;
                    }
                    currMaxArea++;
                    grid[currI][currJ] = 0;
                    for (int[] moveIndex : moveIndexArray) {
    
    
                        stack.add(new int[]{
    
    currI + moveIndex[0], currJ + moveIndex[1]});
                    }
                }
                maxArea = Math.max(currMaxArea, maxArea);
            }
        }

        return maxArea;
    }

}