From 154a744fdc59fc1b6d8ae4bdef29c6910ce846e0 Mon Sep 17 00:00:00 2001 From: fanxb Date: Fri, 17 Sep 2021 23:10:28 +0800 Subject: [PATCH] add --- 5.leetcode/src/com/fanxb/common/Q120.java | 46 ++++++ 5.leetcode/src/com/fanxb/common/Q232.java | 133 ++++++++++++++++++ 5.leetcode/src/com/fanxb/common/Q239.java | 52 +++++++ 5.leetcode/src/com/fanxb/common/Q300.java | 32 +++++ 5.leetcode/src/com/fanxb/common/Q5.java | 48 +++++++ 5.leetcode/src/com/fanxb/common/Q72.java | 46 ++++++ 5.leetcode/src/com/fanxb/common/Q84.java | 46 ++++++ .../src/com/fanxb/common/offer/Q52.java | 65 +++++++++ 8 files changed, 468 insertions(+) create mode 100644 5.leetcode/src/com/fanxb/common/Q120.java create mode 100644 5.leetcode/src/com/fanxb/common/Q232.java create mode 100644 5.leetcode/src/com/fanxb/common/Q239.java create mode 100644 5.leetcode/src/com/fanxb/common/Q300.java create mode 100644 5.leetcode/src/com/fanxb/common/Q5.java create mode 100644 5.leetcode/src/com/fanxb/common/Q72.java create mode 100644 5.leetcode/src/com/fanxb/common/Q84.java create mode 100644 5.leetcode/src/com/fanxb/common/offer/Q52.java diff --git a/5.leetcode/src/com/fanxb/common/Q120.java b/5.leetcode/src/com/fanxb/common/Q120.java new file mode 100644 index 0000000..99b1d43 --- /dev/null +++ b/5.leetcode/src/com/fanxb/common/Q120.java @@ -0,0 +1,46 @@ +package com.fanxb.common; + +import java.util.Arrays; +import java.util.List; + +/** + * @author fanxb + * Date: 2020/6/9 15:10 + */ +public class Q120 { + + public int minimumTotal(List> triangle) { + int lineNum = triangle.size(); + int[][] dp = new int[lineNum][triangle.get(lineNum - 1).size()]; + for (int i = 0; i < lineNum; i++) { + List line = triangle.get(i); + for (int j = 0; j < i + 1; j++) { + if (i == 0) { + dp[i][j] = line.get(j); + } else if (j == 0) { + dp[i][j] = dp[i - 1][j] + line.get(j); + } else if (j == line.size() - 1) { + dp[i][j] = dp[i - 1][j - 1] + line.get(j); + } else { + dp[i][j] = Math.min(dp[i - 1][j - 1], dp[i - 1][j]) + line.get(j); + } + } + } + int min = dp[lineNum - 1][0]; + for (int i = 1; i < lineNum; i++) { + if (dp[lineNum - 1][i] < min) { + min = dp[lineNum - 1][i]; + } + } + return min; + } + + public static void main(String[] args) { + List l1 = Arrays.asList(2); + List l2 = Arrays.asList(3, 4); + List l3 = Arrays.asList(6, 5, 7); + List l4 = Arrays.asList(4, 1, 8, 3); + List> l5 = Arrays.asList(Arrays.asList(-10)); + System.out.println(new Q120().minimumTotal(l5)); + } +} diff --git a/5.leetcode/src/com/fanxb/common/Q232.java b/5.leetcode/src/com/fanxb/common/Q232.java new file mode 100644 index 0000000..e04fe0f --- /dev/null +++ b/5.leetcode/src/com/fanxb/common/Q232.java @@ -0,0 +1,133 @@ +package com.fanxb.common; + +import java.util.Stack; + +/** + * @author fanxb + * @date 2021-08-31-下午4:50 + */ +public class Q232 { + + public static void main(String[] args) { + BetterMyQueue myQueue = new BetterMyQueue(); + myQueue.push(1); + myQueue.push(2); + System.out.println(myQueue.peek()); + System.out.println(myQueue.pop()); + System.out.println(myQueue.empty()); + + } + + /** + * main,每次push元素都放到main中，并把顺序排列好，方法是先把现有元素转移到help中，然后将新元素放到main里，再把help里的元素转移回来 + * + * @author fanxb + * @date 2021/8/31 下午5:08 + */ + private static class MyQueue { + + private Stack main; + private Stack help; + + + /** + * Initialize your data structure here. + */ + public MyQueue() { + main = new Stack<>(); + help = new Stack<>(); + } + + /** + * Push element x to the back of queue. + */ + public void push(int x) { + while (!main.isEmpty()) { + help.push(main.pop()); + } + main.push(x); + while (!help.isEmpty()) { + main.push(help.pop()); + } + } + + /** + * Removes the element from in front of queue and returns that element. + */ + public int pop() { + return main.pop(); + } + + /** + * Get the front element. + */ + public int peek() { + return main.peek(); + } + + /** + * Returns whether the queue is empty. + */ + public boolean empty() { + return main.isEmpty(); + } + } + + /** + * @author fanxb + * @date 2021/8/31 下午5:08 + */ + private static class BetterMyQueue { + + private Stack input; + private Stack output; + + + /** + * Initialize your data structure here. + */ + public BetterMyQueue() { + input = new Stack<>(); + output = new Stack<>(); + } + + /** + * Push element x to the back of queue. + */ + public void push(int x) { + input.push(x); + } + + /** + * Removes the element from in front of queue and returns that element. + */ + public int pop() { + if (output.isEmpty()) { + while (!input.empty()) { + output.push(input.pop()); + } + } + return output.pop(); + } + + /** + * Get the front element. + */ + public int peek() { + if (output.isEmpty()) { + while (!input.empty()) { + output.push(input.pop()); + } + } + return output.peek(); + } + + /** + * Returns whether the queue is empty. + */ + public boolean empty() { + return input.isEmpty(); + } + } + +} diff --git a/5.leetcode/src/com/fanxb/common/Q239.java b/5.leetcode/src/com/fanxb/common/Q239.java new file mode 100644 index 0000000..ac077d1 --- /dev/null +++ b/5.leetcode/src/com/fanxb/common/Q239.java @@ -0,0 +1,52 @@ +package com.fanxb.common; + +import java.util.*; +import java.util.stream.Collectors; + +/** + * 定义转移方程dp[i][j]为长度为i+1的窗口在位置j的最大值 + * 已知dp[0][j]=num[j] + * 转移方程dp[i][j]=max(dp[i-1][j],num[i+j]) + * + * @author fanxb + * @date 2021-08-31-下午11:15 + */ +public class Q239 { + + public int[] maxSlidingWindow(int[] nums, int k) { + //使用链表，构造一个递减的单调链表 + LinkedList indexList = new LinkedList<>(); + int[] res = new int[nums.length - k + 1]; + for (int i = 0; i < nums.length; i++) { + while (!indexList.isEmpty() && nums[indexList.peekLast()] < nums[i]) { + indexList.removeLast(); + } + indexList.addLast(i); + if (indexList.getFirst() < i - k + 1) { + indexList.removeFirst(); + } + if (i >= k - 1) { + res[i - k + 1] = nums[indexList.getFirst()]; + } + } + return res; + } + + public int[] lowMaxSlidingWindow(int[] nums, int k) { + int n = nums.length; + int[] current = Arrays.copyOf(nums, n - k + 1); + for (int i = 1; i < k; i++) { + for (int j = 0; j < n - k + 1; j++) { + if (nums[i + j] > current[j]) { + current[j] = nums[i + j]; + } + } + } + return current; + } + + + public static void main(String[] args) { + System.out.println(Arrays.toString(new Q239().maxSlidingWindow(new int[]{-7, -8, 7, 5, 7, 1, 6, 0}, 4))); + } +} diff --git a/5.leetcode/src/com/fanxb/common/Q300.java b/5.leetcode/src/com/fanxb/common/Q300.java new file mode 100644 index 0000000..321d33c --- /dev/null +++ b/5.leetcode/src/com/fanxb/common/Q300.java @@ -0,0 +1,32 @@ +package com.fanxb.common; + +import java.util.Stack; + +/** + * 定义dp[i]为以nums[i]结尾的子序列最大长度 + * + * @author fanxb + * @date 2021-08-31-下午11:15 + */ +public class Q300 { + + public int lengthOfLIS(int[] nums) { + int n = nums.length, res = 1; + int[] dp = new int[n]; + dp[0] = 1; + for (int i = 1; i < n; i++) { + dp[i] = 1; + for (int j = 0; j < i; j++) { + if (nums[i] > nums[j]) { + dp[i] = Math.max(dp[i], dp[j] + 1); + } + } + res = Math.max(res, dp[i]); + } + return res; + } + + public static void main(String[] args) { + System.out.println(new Q300().lengthOfLIS(new int[]{0, 1, 0, 3, 2, 3})); + } +} diff --git a/5.leetcode/src/com/fanxb/common/Q5.java b/5.leetcode/src/com/fanxb/common/Q5.java new file mode 100644 index 0000000..dbb3a12 --- /dev/null +++ b/5.leetcode/src/com/fanxb/common/Q5.java @@ -0,0 +1,48 @@ +package com.fanxb.common; + +/** + * 定义dp[i][j]表示从i到j的字符串是否为回文串 + * 已知如下情况： + * 1. 当j-i==0时，dp[i][j]是回文串 + * 2. 当j-i==1时，判断s[1]是否等于s[j] + * 3. dp[i][j]=dp[i+1][j-1] && s[i]==s[j] + * 注意坑点：由于第三个转移情况是从i到i+1所以循环的处理很重要，不能直接循环i从0-》n,j从i到n,这样会出现dp[i+1][j-1]的状态还不知道的情况 + * + * @author fanxb + * @date 2021-08-31-下午10:31 + */ +public class Q5 { + + public String longestPalindrome(String s) { + int n = s.length(), max = 0, resI = 0, resJ = 0; + if (n < 2) { + return s; + } + boolean[][] dp = new boolean[n][n]; + //先从长度为1的字符串开始处理 + for (int length = 1; length <= s.length(); length++) { + //i左边界，j右边界 + for (int i = 0; i < s.length(); i++) { + int j = i + length - 1; + if (j >= s.length()) { + continue; + } + if (length == 1) { + dp[i][j] = true; + } else if (s.charAt(i) == s.charAt(j)) { + dp[i][j] = length == 2 || dp[i + 1][j - 1]; + } + if (dp[i][j] && j - i + 1 > max) { + max = j - i + 1; + resI = i; + resJ = j; + } + } + } + return s.substring(resI, resJ + 1); + } + + public static void main(String[] args) { + System.out.println(new Q5().longestPalindrome("babad")); + } +} diff --git a/5.leetcode/src/com/fanxb/common/Q72.java b/5.leetcode/src/com/fanxb/common/Q72.java new file mode 100644 index 0000000..aca3f4b --- /dev/null +++ b/5.leetcode/src/com/fanxb/common/Q72.java @@ -0,0 +1,46 @@ +package com.fanxb.common; + +/** + * 编辑距离，可以对任意一个单词增加一个字母；删除一个字母；替换一个字母； + * a增加一个字母相当于b删除一个字母 + * b增加一个字母相当于a删除一个字母 + * a替换一个字母相当于b替换一个字母 + *

+ * 字符串a,字符串b + *

+ * 定义dp[i][j]为a中前i个字母变化为b中前j个字母需要的步骤 + * 考虑上面三种情况，存在以下三种转移情况 + * dp[i][j]=dp[i-1][j]+1;字母a增加一个字母 + * dp[i][j]=dp[i][j-1]+1;字母b增加一个字母 + * dp[i][j]=dp[i-1][j-1]+(a[i]==a[j]);字母替换，由于a[i],a[j]可能相同，不需要替换，所以不一定要走替换这一步 + *

+ * 极端情况： + * dp[0][j]=j; + * dp[i][0]=i; + * + * @author fanxb + * @date 2021-08-31-下午10:15 + */ +public class Q72 { + + public int minDistance(String word1, String word2) { + int length1 = word1.length(), length2 = word2.length(); + int[][] dp = new int[length1 + 1][length2 + 1]; + for (int i = 0; i <= length1; i++) { + for (int j = 0; j <= length2; j++) { + if (i == 0) { + dp[i][j] = j; + } else if (j == 0) { + dp[i][j] = i; + } else { + dp[i][j] = Math.min(dp[i - 1][j] + 1, Math.min(dp[i][j - 1] + 1, dp[i - 1][j - 1] + (word1.charAt(i - 1) == word2.charAt(j - 1) ? 0 : 1))); + } + } + } + return dp[length1][length2]; + } + + public static void main(String[] args) { + System.out.println(new Q72().minDistance("horse", "ros")); + } +} diff --git a/5.leetcode/src/com/fanxb/common/Q84.java b/5.leetcode/src/com/fanxb/common/Q84.java new file mode 100644 index 0000000..f0677d2 --- /dev/null +++ b/5.leetcode/src/com/fanxb/common/Q84.java @@ -0,0 +1,46 @@ +package com.fanxb.common; + +import java.util.Arrays; +import java.util.LinkedList; +import java.util.Stack; + +/** + * @author fanxb + * @date 2021-08-31-下午11:15 + */ +public class Q84 { + + public int largestRectangleArea(int[] heights) { + int n = heights.length; + Stack stack = new Stack<>(); + int res = 0; + for (int i = 0; i < n; i++) { + int currentHeight = heights[i]; + if (!stack.isEmpty()) { + //说明下一个是更小的，一定能确定一些高度的面积 + while (!stack.isEmpty() && heights[stack.peek()] > currentHeight) { + int height = heights[stack.pop()]; + while (!stack.isEmpty() && heights[stack.peek()] == height) { + stack.pop(); + } + int width = stack.isEmpty() ? i : (i - stack.peek() - 1); + res = Math.max(res, height * width); + } + } + stack.push(i); + } + while (!stack.isEmpty()) { + int height = heights[stack.pop()]; + while (!stack.isEmpty() && heights[stack.peek()] == height) { + stack.pop(); + } + int width = stack.isEmpty() ? n : (n - stack.peek() - 1); + res = Math.max(res, height * width); + } + return res; + } + + public static void main(String[] args) { + System.out.println(new Q84().largestRectangleArea(new int[]{2, 1, 0, 2})); + } +} diff --git a/5.leetcode/src/com/fanxb/common/offer/Q52.java b/5.leetcode/src/com/fanxb/common/offer/Q52.java new file mode 100644 index 0000000..28fbba9 --- /dev/null +++ b/5.leetcode/src/com/fanxb/common/offer/Q52.java @@ -0,0 +1,65 @@ +package com.fanxb.common.offer; + +import java.util.HashMap; +import java.util.HashSet; +import java.util.Map; +import java.util.Set; + +/** + * 两数相加 + * + * @author fanxb + * @date 2021/6/1 + **/ +public class Q52 { + + public static class ListNode { + int val; + ListNode next; + + ListNode(int x) { + val = x; + next = null; + } + } + + public ListNode getIntersectionNode(ListNode headA, ListNode headB) { + if (headA == null || headB == null) { + return null; + } + Set map = new HashSet<>(128); + while (headA != null) { + map.add(headA); + headA = headA.next; + } + while (headB != null) { + if (map.contains(headB)) { + return headB; + } + headB = headB.next; + } + return null; + } + + public static void main(String[] args) { + ListNode a1 = new ListNode(1); + ListNode a2 = new ListNode(2); + ListNode a3 = new ListNode(3); + ListNode a4 = new ListNode(4); + ListNode a5 = new ListNode(5); + ListNode a6 = new ListNode(6); + ListNode b1 = new ListNode(7); + ListNode b2 = new ListNode(8); + ListNode b3 = new ListNode(9); + a1.next = a2; + a2.next = a3; + a3.next = a4; + a4.next = a5; + a5.next = a6; + b1.next = b2; + b2.next = b3; + b3.next = a4; + + System.out.println(new Q52().getIntersectionNode(a1, b1).val); + } +}