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class Solution {
public int add(int a, int b) {
int m = a ^ b; //不进位加法
int n = (a & b) << 1; //进位
while (n != 0) {
int temp = n ^ m;
n = (m & n) << 1;
m = temp;
}
return m;
}
}
class Solution {
public int[] smallestK(int[] arr, int k) {
if (k >= arr.length) {
return arr;
}
int low = 0;
int high = arr.length - 1;
while (low < high) {
int pos = partition(arr, low, high);
if (pos == k - 1) {
break;
} else if (pos < k - 1) {
low = pos + 1;
} else {
high = pos - 1;
}
}
int[] dest = new int[k];
System.arraycopy(arr, 0, dest, 0, k);
return dest;
}
private int partition(int[] arr, int low, int high) {
int pivot = arr[low];
while (low < high) {
while (low < high && arr[high] >= pivot) {
high--;
}
arr[low] = arr[high];
while (low < high && arr[low] <= pivot) {
low++;
}
arr[high] = arr[low];
}
arr[low] = pivot;
return low;
}
}
class Solution {
public int smallestDifference(int[] a, int[] b) {
long result = Integer.MAX_VALUE;
Arrays.sort(a);
Arrays.sort(b);
for (int i = 0, j = 0; i < a.length && j < b.length; ) {
result = Math.min(result, Math.abs((long) a[i] - b[j]));
if (a[i] < b[j]) {
i++;
} else {
j++;
}
}
return (int) result;
}
}
将驼峰命名转为小写下划线命名
LeetCode转化为leet_code，LeetHTTPBack转化为leet_http_back
# -*- coding: utf-8 -*-
def get_trans_name(text):
length=len(text)
lst=[]
for i in range(length):
# 前一个字母大写，后一个字母小写，将该字母从大写转换成小写
if i+1<length and text[i].isupper() and not text[i+1].isupper():
lst.append(text[i].lower())
else:
lst.append(text[i])
# 前一个字母是小写，后一个字母是大写的情景
if not text[i].isupper() and i+1<length and text[i+1].isupper():
lst.append("_")
# 前两个字母是大写，后一个字母是小写的情景
if text[i].isupper() and i+2<length and text[i+1].isupper() and not text[i+2].isupper():
lst.append("_")
return "".join(lst)
if __name__ == '__main__':
print(get_trans_name("LeetCode"))
print(get_trans_name("LeetHTTPBack"))
字符串相减
public class SubString {
/**
* 若a字符串表示的数字小于b字符串表示的数字则返回true
*
* @param a
* @param b
* @return
*/
public static boolean isLess(String a, String b) {
// 由于是大数，考虑转成字符串处理
// 长度更长的字符串，数一定更大
// 当长度一样的就去比较字典序
if (a.length() == b.length()) {
if (a.compareTo(b) < 0) {
return true;
} else if (a.compareTo(b) >= 0) {
return false;
}
}
return a.length() < b.length();
}
/**
* 大数减小数
* @param a
* @param b
* @return
*/
public static String sub(String a, String b) {
StringBuilder ans = new StringBuilder();
int borrow = 0;
int i = a.length() - 1, j = b.length() - 1;
while (i >= 0 || j >= 0) {
int x = i >= 0 ? (a.charAt(i) - '0') : 0;
int y = j >= 0 ? (b.charAt(j) - '0') : 0;
int z = (x - borrow - y + 10) % 10;
ans.append(z);
borrow = x - borrow - y < 0 ? 1 : 0;
i--;
j--;
}
ans.reverse();
// 删除前导零，边界是 ans.length()-1, 防止当 ans 为 "0000" 时，清空
// 121-120=001 需要删除前导0
// 121-121=000 不能把所有 0 都删掉
int pos = 0;
while (pos < ans.length()-1 && ans.charAt(pos) == '0') {
pos++;
}
return ans.toString().substring(pos);
}
/**
* 给定两个字符串形式的非负整数num1和num2，计算它们的差
* 注意：
* num1 和num2 都只会包含数字 0-9
* num1 和num2 都不包含任何前导零
* 你不能使用任何內建 BigInteger 库
* @param a
* @param b
* @return
*/
public static String subString(String a, String b) {
String res;
if (isLess(a, b)) {
res = sub(b, a);
// 结果为 0 时，不加负号
if (res != "0") {
res = "-" + res;
}
} else {
res = sub(a, b);
}
return res;
}
public static void main(String[] args) {
System.out.println(subString("121", "120"));
System.out.println(subString("121", "121"));
}
}
字符串相减（36进制）
public class Sub36 {
public char getChar(int n) {
if (n <= 9) {
return (char)(n + '0');
} else {
return (char)(n - 10 + 'a');
}
}
public int getInt(char c) {
if (c >= '0' && c <= '9') {
return c - '0';
} else {
return c - 'a' + 10;
}
}
public String sub(String a, String b) {
int borrow = 0;
int i = a.length() - 1;
int j = b.length() - 1;
char[] ca = a.toCharArray();
char[] cb = b.toCharArray();
StringBuilder res = new StringBuilder();
while (i >= 0 || j >= 0) {
int x = i >= 0 ? getInt(ca[i]) : 0;
int y = j >= 0 ? getInt(cb[i]) : 0;
int z = (x - borrow - y + 36) % 36;
res.append(getChar(z));
borrow = x - borrow - y < 0 ? 1 : 0;
i--;
j--;
}
res.reverse();
// 删除前导0。注意：循环条件是res.size()-1是为防止"0000"的情况
int pos;
for (pos = 0; pos < res.length() - 1; pos++) {
if (res.charAt(pos) != '0') {
break;
}
}
return res.toString().substring(pos);
}
boolean isLess(String a, String b) {
if (a.length() == b.length()) {
return a.compareTo(b) < 0;
}
return a.length() < b.length();
}
public String subString(String num1, String num2) {
if (isLess(num1, num2)) {
String res = sub(num2, num1);
return "-" + res;
}
return sub(num1, num2);
}
public static void main(String[] args) {
String num1 = "48";
String num2 = "2x";
Sub36 sub36 = new Sub36();
System.out.println(sub36.subString(num1, num2));
}
}