diff --git a/src/class02/Code01_ReverseList.java b/src/class02/Code01_ReverseList.java index dcddf8a..df53140 100644 --- a/src/class02/Code01_ReverseList.java +++ b/src/class02/Code01_ReverseList.java @@ -24,6 +24,9 @@ public class Code01_ReverseList { } } + // head + // a -> b -> c -> null + // c -> b -> a -> null public static Node reverseLinkedList(Node head) { Node pre = null; Node next = null; diff --git a/src/class02/Code02_DeleteGivenValue.java b/src/class02/Code02_DeleteGivenValue.java index 713ff66..c928085 100644 --- a/src/class02/Code02_DeleteGivenValue.java +++ b/src/class02/Code02_DeleteGivenValue.java @@ -11,6 +11,7 @@ public class Code02_DeleteGivenValue { } } + // head = removeValue(head, 2); public static Node removeValue(Node head, int num) { // head来到第一个不需要删的位置 while (head != null) { @@ -19,6 +20,8 @@ public class Code02_DeleteGivenValue { } head = head.next; } + // 1 ) head == null + // 2 ) head != null Node pre = head; Node cur = head; while (cur != null) { diff --git a/src/class02/Code04_RingArray.java b/src/class02/Code04_RingArray.java index b28c2b7..4b67c7b 100644 --- a/src/class02/Code04_RingArray.java +++ b/src/class02/Code04_RingArray.java @@ -4,8 +4,8 @@ public class Code04_RingArray { public static class MyQueue { private int[] arr; - private int pushi; - private int polli; + private int pushi;// end + private int polli;// begin private int size; private final int limit; @@ -19,7 +19,7 @@ public class Code04_RingArray { public void push(int value) { if (size == limit) { - throw new RuntimeException("栈满了，不能再加了"); + throw new RuntimeException("队列满了，不能再加了"); } size++; arr[pushi] = value; @@ -28,7 +28,7 @@ public class Code04_RingArray { public int pop() { if (size == 0) { - throw new RuntimeException("栈空了，不能再拿了"); + throw new RuntimeException("队列空了，不能再拿了"); } size--; int ans = arr[polli]; diff --git a/src/class02/Code08_GetMax.java b/src/class02/Code08_GetMax.java index cd7141f..fde30b3 100644 --- a/src/class02/Code08_GetMax.java +++ b/src/class02/Code08_GetMax.java @@ -9,9 +9,12 @@ public class Code08_GetMax { // arr[L..R]范围上求最大值 L ... R N public static int process(int[] arr, int L, int R) { - if (L == R) { // arr[L..R]范围上只有一个数，直接返回，base case + // arr[L..R]范围上只有一个数，直接返回，base case + if (L == R) { return arr[L]; } + // L...R 不只一个数 + // mid = (L + R) / 2 int mid = L + ((R - L) >> 1); // 中点 1 int leftMax = process(arr, L, mid); int rightMax = process(arr, mid + 1, R); diff --git a/src/class02/HashMapAndSortedMap.java b/src/class02/HashMapAndSortedMap.java index 717b81b..6a7477a 100644 --- a/src/class02/HashMapAndSortedMap.java +++ b/src/class02/HashMapAndSortedMap.java @@ -5,16 +5,39 @@ import java.util.HashSet; import java.util.TreeMap; public class HashMapAndSortedMap { - - - public static class Node{ + + public static class Node { public int value; + public Node(int v) { - value = v; + value = v; } } - + + public static class Zuo { + public int value; + + public Zuo(int v) { + value = v; + } + } + public static void main(String[] args) { + + HashMap test = new HashMap<>(); + Integer a = 19000000; + Integer b = 19000000; + System.out.println(a == b); + + test.put(a, "我是3"); + System.out.println(test.containsKey(b)); + + Zuo z1 = new Zuo(1); + Zuo z2 = new Zuo(1); + HashMap test2 = new HashMap<>(); + test2.put(z1, "我是z1"); + System.out.println(test2.containsKey(z2)); + // UnSortedMap HashMap map = new HashMap<>(); map.put(1000000, "我是1000000"); @@ -24,58 +47,52 @@ public class HashMapAndSortedMap { map.put(5, "我是5"); map.put(6, "我是6"); map.put(1000000, "我是1000001"); - + System.out.println(map.containsKey(1)); System.out.println(map.containsKey(10)); - + System.out.println(map.get(4)); System.out.println(map.get(10)); - + map.put(4, "他是4"); System.out.println(map.get(4)); - + map.remove(4); System.out.println(map.get(4)); - - - - // key - HashSet set = new HashSet<>(); + + // key + HashSet set = new HashSet<>(); set.add("abc"); set.contains("abc"); set.remove("abc"); - + // 哈希表，增、删、改、查，在使用时，O（1） - - + System.out.println("====================="); - - - int a = 100000; - int b = 100000; - System.out.println(a == b); - + Integer c = 100000; Integer d = 100000; System.out.println(c.equals(d)); - - Integer e = 127; // - 128 ~ 127 + + Integer e = 127; // - 128 ~ 127 Integer f = 127; System.out.println(e == f); - - - + HashMap map2 = new HashMap<>(); Node node1 = new Node(1); Node node2 = node1; map2.put(node1, "我是node1"); map2.put(node2, "我是node1"); System.out.println(map2.size()); - + System.out.println("======================"); - + + // TreeMap 有序表：接口名 + // 红黑树、avl、sb树、跳表 + // O(logN) + System.out.println("有序表测试开始"); TreeMap treeMap = new TreeMap<>(); - + treeMap.put(3, "我是3"); treeMap.put(4, "我是4"); treeMap.put(8, "我是8"); @@ -86,27 +103,26 @@ public class HashMapAndSortedMap { System.out.println(treeMap.containsKey(1)); System.out.println(treeMap.containsKey(10)); - + System.out.println(treeMap.get(4)); System.out.println(treeMap.get(10)); - + treeMap.put(4, "他是4"); System.out.println(treeMap.get(4)); - - treeMap.remove(4); + + // treeMap.remove(4); System.out.println(treeMap.get(4)); - + + System.out.println("新鲜："); + System.out.println(treeMap.firstKey()); System.out.println(treeMap.lastKey()); // <= 4 System.out.println(treeMap.floorKey(4)); // >= 4 System.out.println(treeMap.ceilingKey(4)); - - // O(logN) - + // O(logN) + } - - - + } diff --git a/src/class03/Code03_ReversePair.java b/src/class03/Code03_ReversePair.java new file mode 100644 index 0000000..1c3f90b --- /dev/null +++ b/src/class03/Code03_ReversePair.java @@ -0,0 +1,130 @@ +package class03; + +public class Code03_ReversePair { + + public static int reverPairNumber(int[] arr) { + if (arr == null || arr.length < 2) { + return 0; + } + return process(arr, 0, arr.length - 1); + } + + // arr[L..R]既要排好序，也要求逆序对数量返回 + // 所有merge时，产生的逆序对数量，累加，返回 + // 左 排序 merge并产生逆序对数量 + // 右 排序 merge并产生逆序对数量 + public static int process(int[] arr, int l, int r) { + if (l == r) { + return 0; + } + // l < r + int mid = l + ((r - l) >> 1); + return process(arr, l, mid) + process(arr, mid + 1, r) + merge(arr, l, mid, r); + } + + public static int merge(int[] arr, int L, int m, int r) { + int[] help = new int[r - L + 1]; + int i = help.length - 1; + int p1 = m; + int p2 = r; + int res = 0; + while (p1 >= L && p2 > m) { + res += arr[p1] > arr[p2] ? (p2 - m) : 0; + help[i--] = arr[p1] > arr[p2] ? arr[p1--] : arr[p2--]; + } + while (p1 >= L) { + help[i--] = arr[p1--]; + } + while (p2 > m) { + help[i--] = arr[p2--]; + } + for (i = 0; i < help.length; i++) { + arr[L + i] = help[i]; + } + return res; + } + + // for test + public static int comparator(int[] arr) { + int ans = 0; + for (int i = 0; i < arr.length; i++) { + for (int j = i + 1; j < arr.length; j++) { + if (arr[i] > arr[j]) { + ans++; + } + } + } + return ans; + } + + // for test + public static int[] generateRandomArray(int maxSize, int maxValue) { + int[] arr = new int[(int) ((maxSize + 1) * Math.random())]; + for (int i = 0; i < arr.length; i++) { + arr[i] = (int) ((maxValue + 1) * Math.random()) - (int) (maxValue * Math.random()); + } + return arr; + } + + // for test + public static int[] copyArray(int[] arr) { + if (arr == null) { + return null; + } + int[] res = new int[arr.length]; + for (int i = 0; i < arr.length; i++) { + res[i] = arr[i]; + } + return res; + } + + // for test + public static boolean isEqual(int[] arr1, int[] arr2) { + if ((arr1 == null && arr2 != null) || (arr1 != null && arr2 == null)) { + return false; + } + if (arr1 == null && arr2 == null) { + return true; + } + if (arr1.length != arr2.length) { + return false; + } + for (int i = 0; i < arr1.length; i++) { + if (arr1[i] != arr2[i]) { + return false; + } + } + return true; + } + + // for test + public static void printArray(int[] arr) { + if (arr == null) { + return; + } + for (int i = 0; i < arr.length; i++) { + System.out.print(arr[i] + " "); + } + System.out.println(); + } + + // for test + public static void main(String[] args) { + int testTime = 500000; + int maxSize = 100; + int maxValue = 100; + System.out.println("测试开始"); + for (int i = 0; i < testTime; i++) { + int[] arr1 = generateRandomArray(maxSize, maxValue); + int[] arr2 = copyArray(arr1); + if (reverPairNumber(arr1) != comparator(arr2)) { + System.out.println("Oops!"); + printArray(arr1); + printArray(arr2); + break; + } + } + System.out.println("测试结束"); + } + +} diff --git a/src/class03/Code04_BiggerThanRightTwice.java b/src/class03/Code04_BiggerThanRightTwice.java new file mode 100644 index 0000000..6c6afc1 --- /dev/null +++ b/src/class03/Code04_BiggerThanRightTwice.java @@ -0,0 +1,132 @@ +package class03; + +public class Code04_BiggerThanRightTwice { + + public static int biggerTwice(int[] arr) { + if (arr == null || arr.length < 2) { + return 0; + } + return process(arr, 0, arr.length - 1); + } + + public static int process(int[] arr, int l, int r) { + if (l == r) { + return 0; + } + // l < r + int mid = l + ((r - l) >> 1); + return process(arr, l, mid) + process(arr, mid + 1, r) + merge(arr, l, mid, r); + } + + public static int merge(int[] arr, int L, int m, int r) { + int ans = 0; + int windowR = m + 1; + for (int i = L; i <= m; i++) { + while (windowR <= r && arr[i] > (arr[windowR] << 1)) { + windowR++; + } + ans += windowR - m - 1; + } + int[] help = new int[r - L + 1]; + int i = 0; + int p1 = L; + int p2 = m + 1; + while (p1 <= m && p2 <= r) { + help[i++] = arr[p1] <= arr[p2] ? arr[p1++] : arr[p2++]; + } + while (p1 <= m) { + help[i++] = arr[p1++]; + } + while (p2 <= r) { + help[i++] = arr[p2++]; + } + for (i = 0; i < help.length; i++) { + arr[L + i] = help[i]; + } + return ans; + } + + // for test + public static int comparator(int[] arr) { + int ans = 0; + for (int i = 0; i < arr.length; i++) { + for (int j = i + 1; j < arr.length; j++) { + if (arr[i] > (arr[j] << 1)) { + ans++; + } + } + } + return ans; + } + + // for test + public static int[] generateRandomArray(int maxSize, int maxValue) { + int[] arr = new int[(int) ((maxSize + 1) * Math.random())]; + for (int i = 0; i < arr.length; i++) { + arr[i] = (int) ((maxValue + 1) * Math.random()) - (int) ((maxValue + 1) * Math.random()); + } + return arr; + } + + // for test + public static int[] copyArray(int[] arr) { + if (arr == null) { + return null; + } + int[] res = new int[arr.length]; + for (int i = 0; i < arr.length; i++) { + res[i] = arr[i]; + } + return res; + } + + // for test + public static boolean isEqual(int[] arr1, int[] arr2) { + if ((arr1 == null && arr2 != null) || (arr1 != null && arr2 == null)) { + return false; + } + if (arr1 == null && arr2 == null) { + return true; + } + if (arr1.length != arr2.length) { + return false; + } + for (int i = 0; i < arr1.length; i++) { + if (arr1[i] != arr2[i]) { + return false; + } + } + return true; + } + + // for test + public static void printArray(int[] arr) { + if (arr == null) { + return; + } + for (int i = 0; i < arr.length; i++) { + System.out.print(arr[i] + " "); + } + System.out.println(); + } + + // for test + public static void main(String[] args) { + int testTime = 500000; + int maxSize = 100; + int maxValue = 100; + System.out.println("测试开始"); + for (int i = 0; i < testTime; i++) { + int[] arr1 = generateRandomArray(maxSize, maxValue); + int[] arr2 = copyArray(arr1); + if (biggerTwice(arr1) != comparator(arr2)) { + System.out.println("Oops!"); + printArray(arr1); + printArray(arr2); + break; + } + } + System.out.println("测试结束"); + } + +} diff --git a/src/class03/Code03_PartitionAndQuickSort.java b/src/class03/Code05_PartitionAndQuickSort.java similarity index 98% rename from src/class03/Code03_PartitionAndQuickSort.java rename to src/class03/Code05_PartitionAndQuickSort.java index ae8fa78..0677e28 100644 --- a/src/class03/Code03_PartitionAndQuickSort.java +++ b/src/class03/Code05_PartitionAndQuickSort.java @@ -1,6 +1,6 @@ package class03; -public class Code03_PartitionAndQuickSort { +public class Code05_PartitionAndQuickSort { public static void swap(int[] arr, int i, int j) { int tmp = arr[i]; diff --git a/src/class03/Code04_QuickSortRecursiveAndUnrecursive.java b/src/class03/Code06_QuickSortRecursiveAndUnrecursive.java similarity index 98% rename from src/class03/Code04_QuickSortRecursiveAndUnrecursive.java rename to src/class03/Code06_QuickSortRecursiveAndUnrecursive.java index 9a594ec..f24ac56 100644 --- a/src/class03/Code04_QuickSortRecursiveAndUnrecursive.java +++ b/src/class03/Code06_QuickSortRecursiveAndUnrecursive.java @@ -2,7 +2,7 @@ package class03; import java.util.Stack; -public class Code04_QuickSortRecursiveAndUnrecursive { +public class Code06_QuickSortRecursiveAndUnrecursive { // 荷兰国旗问题 public static int[] netherlandsFlag(int[] arr, int L, int R) {