滑动窗口最大值

img

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
class Solution {
    public int[] maxSlidingWindow(int[] nums, int k) {
        int l = nums.length;
        if (nums == null || l < 2) {
            return nums;
        }
        LinkedList<Integer> list = new LinkedList();
        int[] rlt = new int[l - k + 1];
        for (int i = 0; i < l; i++) {
            while (!list.isEmpty() && nums[list.peekLast()] <= nums[i]) {
                list.pollLast();
            }
            list.addLast(i);
            //窗口满了
            if (i >= k && i - k == list.peek()) {
                list.poll();
            }
            if (i - k + 1 >= 0) {
                rlt[i - k + 1] = nums[list.peek()];
            }
        }
        return rlt;
    }
}

无重复字符的最长子串

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
class Solution {
    public int lengthOfLongestSubstring(String s) {
        int[] last = new int[128];
        for (int i = 0; i < 128; i++) {
            last[i] = -1;
        }
        int n = s.length();
        int res = 0;
        int start = 0;
        for (int i = 0; i < n; i++) {
            int index = s.charAt(i);
            start = Math.max(start, last[index] + 1);
            res = Math.max(res, i - start + 1);
            last[index] = i;
            System.out.println("i:"+i+" start:"+start+" res:"+res);
        }
        return res;
    }
}

找到字符串中所有字母异位词

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
class Solution {
    public List<Integer> findAnagrams(String s, String p) {
        if (s == null || s.length() == 0 || s.length() < p.length()) {
            return new ArrayList<>();
        }
        List<Integer> list = new ArrayList<>();
        // 目标串数组
        int[] pArr = new int[26];
        // 窗口数组
        int[] sArr = new int[26];
        for (int i = 0; i < p.length(); i++) {
            pArr[p.charAt(i) - 'a']++;
            sArr[s.charAt(i) - 'a']++;
        }
        int i = 0, j = p.length();
        while (j < s.length()) {
            if (isSame(pArr, sArr)) {
                list.add(i);
            }
            //左边减
            sArr[s.charAt(i) - 'a']--;
            i++;
            //右边加
            sArr[s.charAt(j) - 'a']++;
            j++;
        }
        if (isSame(pArr, sArr)) {
            list.add(i);
        }
        return list;
    }

    private boolean isSame(int[] arr1, int[] arr2) {
        for (int i = 0; i < arr1.length; i++) {
            if (arr1[i] != arr2[i]) {
                return false;
            }
        }
        return true;
    }
}