目錄
一、數組
1.二維數組的查找
public class Solution {
public boolean Find(int target, int [][] array) {
int rows= array.length;
int cols= array[0].length;
int i =rows -1;
int j = 0;
while( i>=0 && j< cols){
if (target > array[i][j]){
j++;
}
else if (target< array[i][j]){
i--;
}
else
return true;
}
return false;
}
}
2.數組中重複的數字
public class Solution {
// Parameters:
// numbers: an array of integers
// length: the length of array numbers
// duplication: (Output) the duplicated number in the array number,length of duplication array is 1,so using duplication[0] = ? in implementation;
// Here duplication like pointor in C/C++, duplication[0] equal *duplication in C/C++
// 這裏要特別注意~返回任意重複的一個，賦值duplication[0]
// Return value: true if the input is valid, and there are some duplications in the array number
// otherwise false
public boolean duplicate(int numbers[],int length,int [] duplication) {
if(length==0) return false;
int[] count=new int[length];
for(int i=0;i<length;i++){
count[numbers[i]]++;
if(count[numbers[i]]==2) {
duplication[0]=numbers[i];
return true;
}
}
return false;
}
}
3.構建乘積數組
import java.util.ArrayList;
public class Solution {
public int[] multiply(int[] A) {
int l = A.length;
int inst = 1;
int[] left = new int[l];
int[] right = new int[l];
int[] result = new int[l];
left[0] = 1;
for(int i = 1; i < l; i++){
left[i] = left[i-1] * A[i-1];
}
right[l-1] = 1;
for(int i = l-2; i >= 0; i--){
right[i] = right[i+1] * A[i+1];
}
for(int i = 0; i < l; i++){
result[i] = left[i] * right[i];
}
return result;
}
}
二.字符串
1.替換空格
public class Solution {
public String replaceSpace(StringBuffer str) {
// 邊界條件
if (str == null || str.equals("")){
return null;
}
StringBuilder newStr = new StringBuilder();
for (int i=0;i<str.length();i++){
if (str.charAt(i) == ' '){
newStr.append('%');
newStr.append('2');
newStr.append('0');
}else {
newStr.append(str.charAt(i));
}
}
return newStr.toString();
}
}
2.正則表達式匹配
import java.util.Arrays;
public class 字符串_正則表達式匹配 {
public static void main(String[] args){
char[] st1 = {'a','b','c'};
char[] st2 = {'a','b','.'};
System.out.println(match(st1, st2));
}
public static boolean match(char[] str, char[] pattern)
{
if(str.length == 0 && pattern.length == 0){
return true;
}
if(str.length > 0 && pattern.length == 0){
return false;
}
if(pattern.length > 1 && pattern[1] == '*'){
if (str.length > 0 && (str[0] == pattern[0] || pattern[0] == '.')){
return match(str, Arrays.copyOfRange(pattern, 2, pattern.length))
|| match(Arrays.copyOfRange(str, 1, str.length), Arrays.copyOfRange(pattern, 2, pattern.length))
|| match(Arrays.copyOfRange(str, 1, str.length), pattern);
}
else{
return match(str, Arrays.copyOfRange(pattern, 2, pattern.length));
}
}
else{
if(str.length > 0 && (str[0] == pattern[0] || pattern[0] == '.')){
return match(Arrays.copyOfRange(str, 1, str.length), Arrays.copyOfRange(pattern, 1, pattern.length));
}
else{
return false;
}
}
}
}
3.字符流中第一個不重複的字符
import java.util.*;
public class 字符串_字符流中第一個不重複的字符 {
private HashMap<Character, Integer> map=new HashMap();
private ArrayList<Character> list=new ArrayList<Character>();
//Insert one char from stringstream
public void Insert(char ch)
{
if(map.containsKey(ch)){
map.put(ch,map.get(ch)+1);
}else{
map.put(ch,1);
}
list.add(ch);
}
//return the first appearence once char in current stringstream
public char FirstAppearingOnce()
{ char c='#';
for(char key : list){
if(map.get(key)==1){
c=key;
break;
}
}
return c;
}
}
4.表示數值的字符串
import java.util.Arrays;
public class 字符串_表示數值的字符串 {
public static void main(String[] args){
char[] a = {'1','2','3','.','4','5','e','+','6'};
boolean bool =isNumeric(a);
System.out.println(bool);
}
public static boolean isNumeric(char[] str){
if(str.length <= 0){
return false;
}
for(int i = 0; i < str.length; i++){
if(str[i] == 'E'){
str[i] = 'e';
}
}
if(contain(str,'e')){
int index = getindex(str, 'e');
char[] left = Arrays.copyOfRange(str, 0, index);
char[] right = Arrays.copyOfRange(str,index + 1, str.length);
if(contain(right, '.') || right.length == 0){
return false;
}
return isDigit(left) && isDigit(right);
} else{
return isDigit(str);
}
}
public static boolean isDigit(char[] str1){
char[] bz = {'0','1','2','3','4','5','6','7','8','9','+','-','.'};
char[] fh = {'+','-'};
int count = 0;
for(int i = 0; i < str1.length; i++) {
if (contain(bz, str1[i])){
if (str1[i] == '.') {
count += 1;
}
if(contain(fh, str1[i]) && i != 0){
return false;
}
} else{
return false;
}
}
if(count > 1) {
return false;
}
return true;
}
public static boolean contain(char[] a, char b){
for(int i = 0; i < a.length; i++){
if(a[i] == b){
return true;
}
}
return false;
}
public static int getindex(char[] a, char b){
for(int i = 0; i < a.length; i++){
if(a[i] == b){
return i;
}
}
return -1;
}
}