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Commit 18a6ddc

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新增面试题
1 parent cfbce0e commit 18a6ddc

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37 files changed

+1192
-174
lines changed

37 files changed

+1192
-174
lines changed

‎README.md‎

Lines changed: 36 additions & 20 deletions
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@@ -1,4 +1,4 @@
1-
package com.hit.basinfo.base_data_structure;
1+
package com.hit.basinfo.data_structure;
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import com.hit.common.ListNode;
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Original file line numberDiff line numberDiff line change
@@ -1,4 +1,4 @@
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package com.hit.basinfo.base_data_structure;
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package com.hit.basinfo.data_structure;
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33
import com.hit.common.ListNode;
44

‎codes/java/leetcodes/src/main/java/com/hit/basmath/interview/top_interview_questions/easy_collection/array/_122.java‎

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Original file line numberDiff line numberDiff line change
@@ -35,47 +35,6 @@
3535
*/
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public class _122 {
3737
public int maxProfit(int[] prices) {
38-
return calculate(prices, 0);
39-
}
40-
41-
private int calculate(int prices[], int s) {
42-
if (s >= prices.length)
43-
return 0;
44-
int max = 0;
45-
for (int start = s; start < prices.length; start++) {
46-
int maxprofit = 0;
47-
for (int i = start + 1; i < prices.length; i++) {
48-
if (prices[start] < prices[i]) {
49-
int profit = calculate(prices, i + 1) + prices[i] - prices[start];
50-
if (profit > maxprofit)
51-
maxprofit = profit;
52-
}
53-
}
54-
if (maxprofit > max)
55-
max = maxprofit;
56-
}
57-
return max;
58-
}
59-
60-
public int maxProfit2(int[] prices) {
61-
if (prices == null || prices.length == 0) return 0;
62-
int i = 0;
63-
int valley = prices[0];
64-
int peak = prices[0];
65-
int maxprofit = 0;
66-
while (i < prices.length - 1) {
67-
while (i < prices.length - 1 && prices[i] >= prices[i + 1])
68-
i++;
69-
valley = prices[i];
70-
while (i < prices.length - 1 && prices[i] <= prices[i + 1])
71-
i++;
72-
peak = prices[i];
73-
maxprofit += peak - valley;
74-
}
75-
return maxprofit;
76-
}
77-
78-
public int maxProfit3(int[] prices) {
7938
int maxProfit = 0;
8039
for (int i = 1; i < prices.length; i++) {
8140
if (prices[i] > prices[i - 1]) {

‎codes/java/leetcodes/src/main/java/com/hit/basmath/interview/top_interview_questions/hard_collection/array_and_strings/_128.java‎

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Original file line numberDiff line numberDiff line change
@@ -19,22 +19,17 @@
1919
* Explanation: The longest consecutive elements sequence is [1, 2, 3, 4]. Therefore its length is 4.
2020
*/
2121
public class _128 {
22-
2322
public int longestConsecutive(int[] nums) {
2423
int longestStreak = 0;
25-
2624
for (int num : nums) {
2725
int currentNum = num;
2826
int currentStreak = 1;
29-
3027
while (arrayContains(nums, currentNum + 1)) {
3128
currentNum += 1;
3229
currentStreak += 1;
3330
}
34-
3531
longestStreak = Math.max(longestStreak, currentStreak);
3632
}
37-
3833
return longestStreak;
3934
}
4035

‎codes/java/leetcodes/src/main/java/com/hit/basmath/interview/top_interview_questions/hard_collection/design/_146.java‎

Lines changed: 4 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -39,8 +39,7 @@ class DLinkedNode {
3939
}
4040

4141
private Hashtable<Integer, DLinkedNode> cache = new Hashtable<>();
42-
private int size;
43-
private int capacity;
42+
private int size, capacity;
4443
private DLinkedNode head, tail;
4544

4645
private void addNode(DLinkedNode node) {
@@ -49,7 +48,6 @@ private void addNode(DLinkedNode node) {
4948
*/
5049
node.prev = head;
5150
node.next = head.next;
52-
5351
head.next.prev = node;
5452
head.next = node;
5553
}
@@ -60,7 +58,6 @@ private void removeNode(DLinkedNode node) {
6058
*/
6159
DLinkedNode prev = node.prev;
6260
DLinkedNode next = node.next;
63-
6461
prev.next = next;
6562
next.prev = prev;
6663
}
@@ -77,9 +74,9 @@ private DLinkedNode popTail() {
7774
/**
7875
* Pop the current tail.
7976
*/
80-
DLinkedNode res = tail.prev;
81-
removeNode(res);
82-
return res;
77+
DLinkedNode tailNode = tail.prev;
78+
removeNode(tailNode);
79+
return tailNode;
8380
}
8481

8582
public LRUCache(int capacity) {

‎codes/java/leetcodes/src/main/java/com/hit/basmath/interview/top_interview_questions/hard_collection/linked_list/_148.java‎

Lines changed: 3 additions & 13 deletions
Original file line numberDiff line numberDiff line change
@@ -19,24 +19,18 @@
1919
*/
2020
public class _148 {
2121
public ListNode sortList(ListNode head) {
22-
if (head == null || head.next == null)
23-
return head;
24-
22+
if (head == null || head.next == null) return head;
2523
// step 1. cut the list to two halves
2624
ListNode prev = null, slow = head, fast = head;
27-
2825
while (fast != null && fast.next != null) {
2926
prev = slow;
3027
slow = slow.next;
3128
fast = fast.next.next;
3229
}
33-
3430
prev.next = null;
35-
3631
// step 2. sort each half
3732
ListNode l1 = sortList(head);
3833
ListNode l2 = sortList(slow);
39-
4034
// step 3. merge l1 and l2
4135
return merge(l1, l2);
4236
}
@@ -53,12 +47,8 @@ private ListNode merge(ListNode l1, ListNode l2) {
5347
}
5448
p = p.next;
5549
}
56-
if (l1 != null)
57-
p.next = l1;
58-
59-
if (l2 != null)
60-
p.next = l2;
61-
50+
if (l1 != null) p.next = l1;
51+
if (l2 != null) p.next = l2;
6252
return root.next;
6353
}
6454
}

‎codes/java/leetcodes/src/main/java/com/hit/basmath/interview/top_interview_questions/medium_collection/sorting_and_searching/_215.java‎

Lines changed: 2 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -62,14 +62,13 @@ private void swap(int[] A, int i, int j) {
6262
public int findKthLargest2(int[] nums, int k) {
6363
// init heap 'the smallest element first'
6464
PriorityQueue<Integer> heap = new PriorityQueue<>();
65-
6665
// keep k largest elements in the heap
6766
for (int n : nums) {
6867
heap.add(n);
69-
if (heap.size() > k)
68+
if (heap.size() > k) {
7069
heap.poll();
70+
}
7171
}
72-
7372
// output
7473
return heap.poll();
7574
}

‎codes/java/leetcodes/src/main/java/com/hit/basmath/interview/top_interview_questions/medium_collection/sorting_and_searching/_56.java‎

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Original file line numberDiff line numberDiff line change
@@ -25,20 +25,19 @@
2525
*/
2626
public class _56 {
2727
public int[][] merge(int[][] intervals) {
28-
if (intervals.length <= 1) return intervals;
29-
// Sort by ascending starting point
30-
Arrays.sort(intervals, (i1, i2) -> Integer.compare(i1[0], i2[0]));
31-
List<int[]> result = new ArrayList<>();
28+
if (intervals.length < 1) return intervals;
29+
Arrays.sort(intervals, (a, b) -> Integer.compare(a[0], b[0]));
30+
List<int[]> ans = new ArrayList<>();
3231
int[] newInterval = intervals[0];
33-
result.add(newInterval);
32+
ans.add(newInterval);
3433
for (int[] interval : intervals) {
35-
if (interval[0] <= newInterval[1]) {// Overlapping intervals, move the end if needed
36-
newInterval[1] = Math.max(newInterval[1], interval[1]);
37-
} else {// Disjoint intervals, add the new interval to the list
34+
if (interval[0] <= newInterval[1]) {
35+
newInterval[1] = Math.max(interval[1], newInterval[1]);
36+
} else {
3837
newInterval = interval;
39-
result.add(newInterval);
38+
ans.add(newInterval);
4039
}
4140
}
42-
return result.toArray(new int[result.size()][]);
41+
return ans.toArray(new int[ans.size()][]);
4342
}
4443
}

‎codes/java/leetcodes/src/main/java/com/hit/basmath/interview/top_interview_questions/medium_collection/trees_and_graphs/_103.java‎

Lines changed: 14 additions & 14 deletions
Original file line numberDiff line numberDiff line change
@@ -31,24 +31,24 @@
3131
*/
3232
public class _103 {
3333
public List<List<Integer>> zigzagLevelOrder(TreeNode root) {
34-
List<List<Integer>> sol = new ArrayList<>();
35-
travel(root, sol, 0);
36-
return sol;
34+
List<List<Integer>> ans = new ArrayList<>();
35+
helper(root, ans, 0);
36+
return ans;
3737
}
3838

39-
private void travel(TreeNode curr, List<List<Integer>> sol, int level) {
39+
private void helper(TreeNode curr, List<List<Integer>> ans, int level) {
4040
if (curr == null) return;
41-
42-
if (sol.size() <= level) {
41+
if (ans.size() <= level) {
4342
List<Integer> newLevel = new LinkedList<>();
44-
sol.add(newLevel);
43+
ans.add(newLevel);
4544
}
46-
47-
List<Integer> collection = sol.get(level);
48-
if (level % 2 == 0) collection.add(curr.val);
49-
else collection.add(0, curr.val);
50-
51-
travel(curr.left, sol, level + 1);
52-
travel(curr.right, sol, level + 1);
45+
List<Integer> collection = ans.get(level);
46+
if (level % 2 == 0) {
47+
collection.add(curr.val);
48+
} else {
49+
collection.add(0, curr.val);
50+
}
51+
helper(curr.left, ans, level + 1);
52+
helper(curr.right, ans, level + 1);
5353
}
5454
}

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