JZ3 数组中重复的数字⭐
1 /*
2 * ① map/set
3 * ② 因为"长度为n的数组里的所有数字都在0到n-1的范围内"
4 * 所以对数组进行调整使得 numbers[idx]==idx
5 * */
6 public class JZ3_1
7 {
8 public static int duplicate(int[] numbers)
9 {
10 for (int idx = 0; idx < numbers.length; idx++)
11 {
12 while (idx != numbers[idx])
13 {
14 if (numbers[idx] == numbers[numbers[idx]])
15 return numbers[idx];
16 int temp = numbers[numbers[idx]];
17 numbers[numbers[idx]] = numbers[idx];
18 numbers[idx] = temp;
19 }
20 }
21 return -1;
22 }
23 }
JZ51 数组中的逆序对
1 /* 归并 */
2 public class JZ51_1
3 {
4 public static int res = 0;
5 public static final int MOD = 1000000007;
6
7 public static int InversePairs(int[] nums)
8 {
9 partition(nums, 0, nums.length - 1);
10 return res % MOD;
11 }
12
13 public static void partition(int[] nums, int left, int right)
14 {
15 if (left < right)
16 {
17 int mid = (left + right) / 2;
18 partition(nums, left, mid);
19 partition(nums, mid + 1, right);
20 merge(nums, left, mid, right);
21 }
22 }
23
24 public static void merge(int[] nums, int left, int mid, int right)
25 {
26 int l = left, r = mid + 1, k = 0;
27 int[] temp = new int[right - left + 1];
28 while (l <= mid && r <= right)
29 {
30 if (nums[l] <= nums[r])
31 {
32 temp[k++] = nums[l];
33 l++;
34 }
35 else
36 {
37 temp[k++] = nums[r];
38 res += (mid - l + 1);
39 res %= MOD;
40 r++;
41 }
42 }
43 while (l <= mid)
44 {
45 temp[k] = nums[l];
46 k++;
47 l++;
48 }
49 while (r <= right)
50 {
51 temp[k] = nums[r];
52 k++;
53 r++;
54 }
55 for (int i = 0; i < k; i++)
56 nums[left + i] = temp[i];
57 }
58 }
59
60 /* ⭐树状数组⭐ */
61 public class JZ51_2
62 {
63 public static int res = 0;
64 public static final int MOD = 1000000007;
65 public static int[] tree;
66
67 public static class KVCLass implements Comparable<KVCLass>
68 {
69 public int value;
70 public int idx;
71
72 KVCLass(int k, int v)
73 {
74 this.value = k;
75 this.idx = v;
76 }
77
78 @Override
79 public int compareTo(KVCLass o)
80 {
81 return value - o.value;
82 }
83 }
84
85 public static int InversePairs(int[] nums)
86 {
87 KVCLass[] temp = new KVCLass[nums.length];
88 tree = new int[nums.length + 1];
89 for (int i = 0; i < nums.length; i++)
90 temp[i] = new KVCLass(nums[i], i + 1);
91 Arrays.sort(temp);
92 for (int i = 0; i < temp.length; i++)
93 {
94 add(temp[i].idx);
95 res = (res + i - sum(temp[i].idx - 1)) % MOD;
96 }
97 return res;
98 }
99
100 private static int sum(int idx)
101 {
102 int ans = 0;
103 while (idx > 0)
104 {
105 ans = (ans + tree[idx]) % MOD;
106 idx -= (idx & (-idx));
107 }
108 return ans;
109 }
110
111 private static void add(int idx)
112 {
113 while (idx < tree.length)
114 {
115 tree[idx] += 1;
116 idx += (idx & (-idx));
117 }
118 }
119 }
JZ40 最小的K个数
1 /* ⭐快排⭐ */
2 public class JZ40_1
3 {
4 public static ArrayList<Integer> GetLeastNumbers_Solution(int[] input, int k)
5 {
6 ArrayList<Integer> res = new ArrayList<>();
7 int left = 0, right = input.length - 1;
8 while (true)
9 {
10 int idx = quickSort(input, left, right);
11 if (idx < k)
12 left = idx + 1;
13 else if (idx > k)
14 right = idx - 1;
15 else
16 break;
17 }
18 for (int i = 0; i < k; i++)
19 {
20 res.add(input[i]);
21 System.out.println(input[i]);
22 }
23 return res;
24 }
25
26 private static int quickSort(int[] input, int left, int right)
27 {
28 if (left >= right) return left;
29 int pivot = input[right], low = left, high = right;
30 while (low < high)
31 {
32 while (low < high && input[low] < pivot) low++;
33 input[high] = input[low];
34 while (low < high && input[high] >= pivot) high--;
35 input[low] = input[high];
36 }
37 input[low] = pivot;
38 return low;
39 }
40 }
41
42 /* 堆 */
43 public class JZ40_2
44 {
45 public static ArrayList<Integer> GetLeastNumbers_Solution(int[] input, int k)
46 {
47 ArrayList<Integer> res = new ArrayList<>();
48 PriorityQueue<Integer> queue = new PriorityQueue<>(k+1, new Comparator<Integer>()
49 {
50 @Override
51 public int compare(Integer o1, Integer o2)
52 {
53 return o2 - o1;
54 }
55 });
56 for (int i = 0; i < input.length && k != 0; i++)
57 {
58 if (i < k)
59 queue.add(input[i]);
60 else
61 {
62 if (input[i] < queue.peek())
63 {
64 queue.poll();
65 queue.add(input[i]);
66 }
67 }
68 }
69 while (!queue.isEmpty())
70 res.add(queue.poll());
71 return res;
72 }
73 }
JZ41 数据流中的中位数⭐
1 /* 堆 */
2 public class JZ41_1
3 {
4 public static PriorityQueue<Integer> minHeap = new PriorityQueue<>();
5 public static PriorityQueue<Integer> maxHeap = new PriorityQueue<>(new Comparator<Integer>()
6 {
7 public int compare(Integer o1, Integer o2)
8 {
9 return o2 - o1;
10 }
11 });
12 public static int count = 0;
13
14 public static void Insert(Integer num)
15 {
16 count++;
17 if (count % 2 != 0)
18 {
19 if (!minHeap.isEmpty() && num > minHeap.peek())
20 {
21 maxHeap.add(minHeap.poll());
22 minHeap.add(num);
23 }
24 else
25 maxHeap.add(num);
26 }
27 else
28 {
29 if (!maxHeap.isEmpty() && num < maxHeap.peek())
30 {
31 minHeap.add(maxHeap.poll());
32 maxHeap.add(num);
33 }
34 else
35 minHeap.add(num);
36 }
37 }
38
39 // public static void Insert(Integer num)
40 // {
41 // count++;
42 // if (count % 2 != 0)
43 // {
44 // minHeap.add(num);
45 // maxHeap.add(minHeap.poll());
46 // }
47 // else
48 // {
49 // maxHeap.add(num);
50 // minHeap.add(maxHeap.poll());
51 // }
52 // }
53
54 public static Double GetMedian()
55 {
56 if (minHeap.size() == maxHeap.size())
57 return (minHeap.peek() + maxHeap.peek()) / 2.0;
58 else
59 return maxHeap.peek() * 1.0;
60 }
61 }
