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leetcode409.java
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71 lines (66 loc) · 2.1 KB
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package leetcode;
import java.util.HashMap;
public class leetcode409 {
/*
* leetcode 409 组成最长回文串
* */
public int longestPalindrome(String s) {
HashMap<String,Integer> map=new HashMap<String,Integer>();
int result=0;
for(char ch:s.toCharArray()){
if(map.containsKey(ch+"")) map.put(ch+"",map.get(ch+"")+1); //计数加+1
else map.put(ch+"",1); //计数1
}
boolean iscontainOdd=false;
for (String str:map.keySet()) {
if (map.get(str)%2==0) result+=map.get(str);
else {
result+=(map.get(str)-1);
iscontainOdd=true;
}
}
return iscontainOdd?result+1:result;
}
/*
* leetcode 42 验证回文串
* */
public boolean isPalindrome(String s) {
s=s.replaceAll(" ","").replaceAll("[^a-zA-Z0-9]", "").toLowerCase(); //替换所有空格
boolean flag=s.length()%2!=1? false:true; //奇数偶数
int temp=0;
temp=s.length()/2;
if(flag){ //奇数
return s.substring(0,temp).equals(new String(new StringBuilder(s.substring(temp+1,s.length())).reverse()));
}else{ //偶数
return s.substring(0,temp).equals(new String(new StringBuilder(s.substring(temp,s.length())).reverse()));
}
}
/*
* leetcode 564 寻找最近的回文数
* 难点在于如何处理Integer的溢出问题
* 贪心法 超时
* */
public String nearestPalindromic(String n) {
int aim=Integer.parseInt(n);
int bigger=aim+1;
int smaller=aim-1;
for (int j = smaller; j >=0 ; --j) {
if (isPalindrome(j+"")){
smaller=j;
break;
}
}
for (int i = bigger;; i++) {
if (isPalindrome(i+"")){
bigger=i;
break;
}
}
return aim-smaller>bigger-aim?bigger+"":smaller+"";
}
public static void main(String[] args) {
System.out.println(
new leetcode409().nearestPalindromic("123")
);
}
}