自己把leetcode的一些基础知识对应的题目总结下来放在了gitee上，希望对大家有帮助。
另外自己写了一些方便大家使用自己的IDE进行调试的工具，也放在了下面。
- 算法知识对应题目列表
- leetcode数据转换工具
- 前言
- 工具
- 字符串转化成数组
- 数组的输出
- 树的操作
- 链表的操作
- 点赞点赞
由于使用leetcode直接写代码，调试的时候总是需要排队，所以个人还是比较喜欢使用IDE进行编码的。但是由于leetcode的数据的格式不能直接复制粘贴，所以写了一些工具进行转化。
字符串转化成数组- 把字符串转化成列表(String类型和int类型)
- 把字符串转化成一维和二维数组(String和int类型)。
由于leetcode中最常见的就是String和int类型的二维数组。所以写一个转换，方便输入数据的时候进行直接复制粘贴，不用在手动转换了。
package leetcode.utils;
import java.util.ArrayList;
import java.util.List;
public class ChangeToArrayOrList {
private static int idx;
private ChangeToArrayOrList() {} // 不提供构对象，只提供方法
@SuppressWarnings("unchecked")
private static List changeToIntList(char[] chars) {
List list = new ArrayList();
if (chars[idx] == '[') {
while(idx < chars.length && chars[idx] == '[') {
idx++; // 去掉左括号
List nlist = changeToIntList(chars);
list.add(nlist);
while(idx < chars.length && (chars[idx] == ']' || chars[idx] == ','))
idx++; // 去掉逗号和右括号
}
} else { // 字母
while(idx < chars.length && Character.isDigit(chars[idx])) {
StringBuilder b = new StringBuilder();
while(Character.isDigit(chars[idx])) {
b.append(chars[idx]);
idx++;
}
list.add(Integer.valueOf(b.toString()));
idx++; // 逗号和右括号去掉
}
}
return list;
}
@SuppressWarnings("unchecked")
private static List changeToStringList(char[] chars) {
List list = new ArrayList();
if (chars[idx] == '[') {
while(idx < chars.length && chars[idx] == '[') {
idx++; // 去掉左括号
List nlist = changeToStringList(chars);
list.add(nlist);
while(idx < chars.length && (chars[idx] == ']' || chars[idx] == ','))
idx++; // 去掉逗号和右括号
}
} else { // 字符串
while(idx < chars.length && (Character.isLetter(chars[idx]) || chars[idx] == '"')) {
StringBuilder b = new StringBuilder();
while(Character.isLetter(chars[idx]) || chars[idx] == '"') {
b.append(chars[idx]);
idx++;
}
list.add(b.toString());
idx++; // 逗号和右括号去掉
}
}
return list;
}
public static List changeToIntList(String s) {
s = s.replace(" ", "");
idx = 0;
// 这里需要先验证是否符合上面两条数据，如果不符合直接返回
if (s.length() == 0)
{
throw new RuntimeException("不是正确的数组类型啊，亲");
}
List list = changeToIntList(s.toCharArray());
return (List)list.get(0);
}
public static List changeToStringList(String s) {
s = s.replace(" ", "");
idx = 0;
// 这里需要先验证是否符合上面两条数据，如果不符合直接返回
if (s.length() == 0)
{
throw new RuntimeException("不是正确的数组类型啊，亲");
}
List list = changeToStringList(s.toCharArray());
return (List)list.get(0);
}
public static int [] changTo1DIntArray(String s) {
s = s.replace(" ", "");
List list = changeToIntList(s);
if (list == null) {
throw new RuntimeException("必须保证是一维数组啊，亲");
}
int [] ans = new int[list.size()];
for (int i = 0; i < list.size(); i++) {
ans[i] = (Integer) list.get(i);
}
return ans;
}
public static int[][] changeTo2DIntArray(String s) {
s = s.replace(" ", "");
List list = changeToIntList(s);
if (list == null || list.size() == 0) {
throw new RuntimeException("必须保证是二维数组啊，亲");
}
List list1 = (List)list.get(0);
int m = list1.size(), n = list.size();
int[][] ans = new int[n][m];
for (int i = 0; i < n; i++) {
list1 = (List)list.get(i);
if (list1.size() > m) {
throw new RuntimeException("数组越界了啊，亲，必须保证维度相同啊");
}
for (int j = 0; j < m; j++) {
ans[i][j] = (Integer) list1.get(j);
}
}
return ans;
}
public static String[] changeTo1DString(String s) {
s = s.replace(" ", "");
List list = changeToStringList(s);
if (list == null) {
throw new RuntimeException("必须保证是一维数组啊，亲");
}
String[] ans = new String[list.size()];
for (int i = 0; i < list.size(); i++) {
ans[i] = (String) list.get(i);
}
return ans;
}
public static String[][] changTo2DString(String s) {
s = s.replace(" ", "");
List list = changeToStringList(s);
if (list == null || list.size() == 0) {
throw new RuntimeException("必须保证是二维数组啊，亲");
}
List list1 = (List)list.get(0);
int m = list1.size(), n = list.size();
String[][] ans = new String[n][m];
for (int i = 0; i < n; i++) {
list1 = (List)list.get(i);
if (list1.size() != m) {
throw new RuntimeException("数组越界了啊，亲，必须保证维度相同啊");
}
for (int j = 0; j < m; j++) {
ans[i][j] = (String) list1.get(j);
}
}
return ans;
}
public static void main(String[] args) {
String s = "[["fda"],["dsfa"]]";
List list = changeToStringList(s);
System.out.println(list);
s = "[[1,1],[2,2],[2,0],[2,4],[3,3],[4,2]]";
list = changeToIntList(s);
System.out.println(s);
int[][]arrs = changeTo2DIntArray(s);
PrintArrays.print2DIntArray(arrs);
s = "[13,43,42,1]";
int[] arr = changTo1DIntArray(s);
System.out.println();
s = "["mass","as","hero","superhero"]";
String[] sArr = changeTo1DString(s);
PrintArrays.print1DObjArray(sArr);
s = "[["mass","as"],["hero","superhero"]]";
String[][] sArrs = changTo2DString(s);
PrintArrays.print2DObjArray(sArrs);
}
}
数组的输出
每次调试的时候，输出一、二维数组，都是一个巨大的负担。
并且Java中数组转化成list还需要强制转换或者使用流操作，特别不爽，还是自己写一个打印的比较爽。
package leetcode.utils;
public class PrintArrays {
private PrintArrays() {}
public static void print2DIntArray(int[][] arr) {
if (arr.length == 0) {
System.out.println("[]");
return ;
}
int n = arr.length, m = arr[0].length;
System.out.print('[');
for (int i = 0; i < n; i++) {
System.out.print('[');
for (int j = 0; j < m; j++) {
System.out.print(arr[i][j]);
if (j != m - 1) System.out.print(',');
else System.out.print(']');
}
if (i != n - 1) System.out.print(',');
else System.out.println(']');
}
}
public static void print1DIntArray(int[] arr) {
System.out.print("[");
for (int i = 0; i < arr.length; i++) {
System.out.print(arr[i]);
if (i != arr.length - 1) System.out.print(",");
else System.out.println("]");
}
}
public static void print1DObjArray(Object[] arr) {
System.out.print("[");
for (int i = 0; i < arr.length; i++) {
System.out.print(arr[i]);
if (i != arr.length - 1) System.out.print(",");
else System.out.println("]");
}
}
public static void print2DObjArray(Object[][] arr) {
if (arr.length == 0) {
throw new RuntimeException("必须是二维数组啊，亲人");
}
int n = arr.length, m = arr[0].length;
System.out.print('[');
for (int i = 0; i < n; i++) {
System.out.print('[');
for (int j = 0; j < m; j++) {
System.out.print(arr[i][j]);
if (j != m - 1) System.out.print(',');
else System.out.print(']');
}
if (i != n - 1) System.out.print(',');
else System.out.println(']');
}
}
public static void main(String[] args) {
int[][] nums = {{323,432},{42,42}};
print2DIntArray(nums);
int[] num = {123,434};
print1DIntArray(num);
}
}
树的操作
暂定
链表的操作妈妈再也不用担心我没法调试列表了。
- 链表的创建
- 链表的遍历
- 链表的反转
package leetcode.utils;
import com.sun.istack.internal.NotNull;
import leetcode.everyDay.April.Exercise25;
import java.util.List;
public class ListNode {
int val;
ListNode next;
ListNode() {
}
ListNode(int val) {
this.val = val;
}
ListNode(int val,ListNode next) {
this.val = val;
this.next = next;
}
private static ListNode createList(int[]list) {
ListNode head = new ListNode();
ListNode p = head;
for (int x: list) {
p.next = new ListNode(x);
p = p.next;
}
return head.next;
}
public static void travelList(@NotNull ListNode h) {
ListNode p = h;
System.out.print("[");
while(p.next != null) {
System.out.print(p.val + ",");
p = p.next;
}
System.out.println(p.val + "]");
}
public ListNode reverseList(ListNode l) {
ListNode head = new ListNode();
ListNode p = l;
while(p != null) {
ListNode t = p;
p = p.next;
t.next = head.next;
head.next = t;
}
return head.next;
}
public static void main(String[] args) {
int[]list = {1,2,3,3,4,4,5};
ListNode h = createList(list);
travelList(h);
}
}
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