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提交说明: 删除了冗余代码，优化了测试用例，并添加了新的解题方法。

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whaifree 2024-04-19 14:58:31 +08:00
parent 3b19c764d8
commit 8749e5b188
6 changed files with 394 additions and 3 deletions
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69
src/main/java/cn/whaifree/leetCode/Dynamic/LeetCode714.java Normal file
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package cn.whaifree.leetCode.Dynamic;
import org.junit.Test;
/**
* @version 1.0
* @Author whai文海
* @Date 2024/4/19 12:27
* @注释
*/
public class LeetCode714 {
@Test
public void test()
{
int[] prices = {1, 3, 2, 8, 4, 9};
int maxProfit = new Solution1().maxProfit(prices, 2);
System.out.println(maxProfit);
}
class Solution {
/**
* dp[i][0] 表示手里没有股票的最大手头持有
* - i-1 就没有 dp[i-1][0]
* - i刚刚卖出 dp[i-1][1] + price[i] - fee
* dp[i][1] 表示手里有股票的最大手头持有
* - i-1 有 dp[i-1][1]
* - i刚刚买入 dp[i-1][0] - price[i] - fee
* @param prices
* @param fee
* @return
*/
public int maxProfit(int[] prices, int fee) {
int[][] dp = new int[prices.length][2];
dp[0][1] = -prices[0] - fee;
for (int i = 1; i < prices.length; i++) {
dp[i][0] = Math.max(dp[i - 1][0], dp[i - 1][1] + prices[i]);
dp[i][1] = Math.max(dp[i - 1][1], dp[i - 1][0] - prices[i] - fee);
}
return dp[prices.length - 1][0];
}
}
class Solution1 {
/**
* dp[i][0] 表示手里没有股票的最大手头持有
* - i-1 就没有 dp[i-1][0]
* - i刚刚卖出 dp[i-1][1] + price[i] - fee
* dp[i][1] 表示手里有股票的最大手头持有
* - i-1 有 dp[i-1][1]
* - i刚刚买入 dp[i-1][0] - price[i] - fee
* @param prices
* @param fee
* @return
*/
public int maxProfit(int[] prices, int fee) {
int[] dp = new int[2];
dp[1] = -prices[0] - fee;
for (int i = 1; i < prices.length; i++) {
dp[0] = Math.max(dp[0], dp[1] + prices[i]);
dp[1] = Math.max(dp[1], dp[0] - prices[i] - fee);
}
return dp[0];
}
}
}

102
src/main/java/cn/whaifree/redo/redo_24_4_20/LeetCode5.java Normal file
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package cn.whaifree.redo.redo_24_4_20;
import org.junit.Test;
/**
* @version 1.0
* @Author whai文海
* @Date 2024/4/19 13:18
* @注释
*/
public class LeetCode5 {
@Test
public void test()
{
String s = "bb";
String s1 = new Solution1().longestPalindrome(s);
System.out.println(s1);
}
class Solution {
/**
* dp[i][j] 表示i-j是不是回文
*
* @param s
* @return
*/
public String longestPalindrome(String s) {
int length = s.length();
boolean[][] dp = new boolean[length][length];
int maxLeft = 0;
int maxRight = 0;
// dp[i][j] 由(i+1)~(j-1)确定，即子串
// 则 dp[i][j] 由dp[i+1][j-1]确定
for (int i = length; i >= 0; i--) {
for (int j = i; j < length; j++) {
if (s.charAt(i) == s.charAt(j)
&& (i == j || i + 1 == j || dp[i + 1][j - 1])
// 一个元素是回文 两个元素也是回文
) {
if ((maxRight - maxLeft) <= j - i) {
maxLeft = i;
maxRight = j;
}
dp[i][j] = true;
} else {
dp[i][j] = false;
}
}
}
return s.substring(maxLeft, maxRight + 1);
}
}
class Solution1 {
/**
*
* @param s
* @return
*/
public String longestPalindrome(String s) {
// 从中间向外扩散获得最长的回文串
int length = s.length();
String maxRes = "";
for (int i = 0; i < length; i++) {
String s1 = maxLengthHuiWen(s, i, i);
String s2 = maxLengthHuiWen(s, i, i + 1);
if (maxRes.length() < s1.length()) {
maxRes = s1;
}
if (maxRes.length() < s2.length()){
maxRes = s2;
}
}
return maxRes;
}
/**
* 向外扩散的两个指针
* @param s
* @param start
* @param end
* @return
*/
public String maxLengthHuiWen(String s, int start, int end) {
int length = s.length();
while (start >= 0 && end < length) {
if (s.charAt(start) != s.charAt(end)) {
break;
}
start--;
end++;
}
return s.substring(start + 1, end);
}
}
}

44
src/main/java/cn/whaifree/redo/redo_24_4_20/LeetCode647.java Normal file
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package cn.whaifree.redo.redo_24_4_20;
import org.junit.Test;
/**
* @version 1.0
* @Author whai文海
* @Date 2024/4/19 14:37
* @注释
*/
public class LeetCode647 {
@Test
public void test()
{
Solution solution = new Solution();
int res = solution.countSubstrings("abc");
System.out.println(res);
}
class Solution {
public int countSubstrings(String s) {
int res = 0;
for (int i = 0; i < s.length(); i++) {
res += count(s, i, i);
res += count(s, i, i + 1);
}
return res;
}
public int count(String s, int start, int end) {
int res = 0;
while (start >= 0 && end < s.length()) {
if (s.charAt(start) != s.charAt(end)) {
break;
}
res++;
start--;
end++;
}
return res;
}
}
}

69
src/main/java/cn/whaifree/redo/redo_24_4_20/LeetCode69.java Normal file
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package cn.whaifree.redo.redo_24_4_20;
import org.junit.Test;
/**
* @version 1.0
* @Author whai文海
* @Date 2024/4/17 11:06
* @注释
*/
public class LeetCode69 {
@Test
public void test()
{
int i = new Solution1().mySqrt(10);
System.out.println(i);
}
class Solution {
/**
* <img src="http://42.192.130.83:9000/picgo/imgs/image-20240417112028966.png">
* x^(1/2) = p
* 1/2 = log x p = ln x / ln p
* ln p = 2 ln x
* p = e^(2lnx)
* @param x
* @return
*/
public int mySqrt(int x) {
if (x == 0) {
return 0;
}
// 用1/2 用例为9会输出2，错误
int exp = (int) Math.exp( 1d/2 * Math.log(x));
if ((long) (exp + 1) * (exp + 1) <= x) { // 8--> exp = 1
return exp + 1;
}
return exp;
}
}
class Solution1 {
/**
* 二分查找 12
* @param x
* @return
*/
public int mySqrt(int x) {
int left = 0;
int right = x;
int ans = 0;
while (left <= right) {
int mid = left + (right - left) / 2;
if ((long) mid * mid > x) {
right = mid - 1;
} else {
ans = mid;
left = mid + 1;
}
}
return ans;
}
}
}

109
src/main/java/cn/whaifree/redo/redo_24_4_20/LeetCode75.java Normal file
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package cn.whaifree.redo.redo_24_4_20;
import org.junit.Test;
import java.util.Arrays;
/**
* @version 1.0
* @Author whai文海
* @Date 2024/4/17 11:38
* @注释
*/
public class LeetCode75 {
@Test
public void test() {
int[] nums = {1, 2, 0};
new Solution1().sortColors(nums);
System.out.println(Arrays.toString(nums));
}
class Solution {
/**
* 0 1 2三个元素，第一次遍历全部把0放前面
* @param nums
*/
public void sortColors(int[] nums) {
int indexZero = 0;
for (int i = 0; i < nums.length; i++) {
if (nums[i] == 0) {
swap(nums, i, indexZero++);
}
}
for (int i = indexZero; i < nums.length; i++) {
if (nums[i] == 1) {
swap(nums, i, indexZero++);
}
}
}
public void swap(int[] nums, int i, int j) {
int temp = nums[i];
nums[i] = nums[j];
nums[j] = temp;
}
}
class Solution1 {
/**
* 双指针：两个指针指向0和1应该swap的地方
* @param nums
*/
public void sortColors(int[] nums) {
int indexZero = 0;
int indexOne = 0;
for (int i = 0; i < nums.length; i++) {
if (nums[i] == 0) {
swap(nums, indexZero, i);
// 此时有可能index0指向的是1，这样交换会把1交换到后面去
// 即交换后的i指向的可能为1
// 需要把这个1给他替换到index1对应的位置
if (indexZero < indexOne) {
swap(nums, i, indexOne);
}
indexOne++;
indexZero++;
}else if (nums[i] == 1){
swap(nums, indexOne++, i);
}
}
}
public void swap(int[] nums, int i, int j) {
int temp = nums[i];
nums[i] = nums[j];
nums[j] = temp;
}
}
class Solution2 {
/**
* 双指针：将所有0变到头部，所有2变到尾部
* @param nums
*/
public void sortColors(int[] nums) {
int index0 = 0;
int index2 = nums.length - 1;
for (int i = 0; i <= index2; i++) {
while (index2 >= i && nums[i] == 2) {
swap(nums, index2--, i);
}
if (nums[i] == 0) {
swap(nums, index0++, i);
}
}
}
public void swap(int[] nums, int i, int j) {
int temp = nums[i];
nums[i] = nums[j];
nums[j] = temp;
}
}
}

4
src/test/java/TestInteger.java
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public class TestInteger {
public static void main(String[] args) {
Integer a = new Integer(100);
Integer b = new Integer(100);
System.out.println(a == b); //false 两个对象，指向
/**
* 0 new #2 <java/lang/Integer>