999. 车的可用捕获量

class Solution {
    public int numRookCaptures(char[][] board) {
        // 定义上下左右四个方向
        int[] dx = {-1, 1, 0, 0};
        int[] dy = {0, 0, -1, 1};
       
        for (int i = 0; i < 8; i++) {
            for (int j = 0; j < 8; j++) {
                // 找到白车所在的位置
                if (board[i][j] == 'R') {
                    // 分别判断白车的上、下、左、右四个方向
                    int res = 0;
                    for (int k = 0; k < 4; k++) {
                        int x = i, y = j;
                        while (true) {
                            x += dx[k];
                            y += dy[k];
                            if (x < 0 || x >= 8 || y < 0 || y >= 8 || board[x][y] == 'B') {
                                break;
                            }
                            if (board[x][y] == 'p') {
                                res++;
                                break;
                            }
                        }
                    }
                    return res;
                }
            }
        }
        return 0;
    }
}

面试题63. 股票的最大利润

class Solution {
    public int maxProfit(int[] prices) {
        if(prices.length<2){
            return 0;
        }
        int min = prices[0];
        int max = prices[1]-min;
        for(int i = 1;i<prices.length-1;i++){
            min = Math.min(min,prices[i]);
            max = Math.max(max,prices[i+1]-min);
        }
        return max<0?0:max;
    }
}

class Solution {
    public int maxProfit(int[] prices) {
        if(prices.length==0) return 0;
        
        int ans=0,min=prices[0],n=prices.length;
        for(int i=0;i<n;i++){
            if(prices[i]<=min) min=prices[i];
            else
                ans=Math.max(ans,prices[i]-min);
        }
        return ans;
    }
}

面试题18. 删除链表的节点

class Solution {
    public ListNode deleteNode(ListNode head, int val) {
        if(head.val == val) return head.next;
        ListNode pre = head, cur = head.next;
        while(cur != null && cur.val != val) {
            pre = cur;
            cur = cur.next;
        }
        pre.next = cur.next;
        return head;
    }
}

class Solution {
    public ListNode deleteNode(ListNode head, int val) {
        ListNode dummyHead = new ListNode(0), pre = dummyHead;
        dummyHead.next = head;
        while(pre.next != null) {
            if(pre.next.val == val) {
                pre.next = pre.next.next;
                break;
            }
            pre = pre.next;
        }
        return dummyHead.next;
    }
}

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