给定一个字符串s,你可以从中删除一些字符,使得剩下的串是一个回文串。如何删除才能使得回文串最长呢?
输出需要删除的字符个数。
输入数据有多组,每组包含一个字符串s,且保证:1<=s.length<=1000.
对于每组数据,输出一个整数,代表最少需要删除的字符个数。
输入例子:
abcda
google
输出例子:
2
2
import java.io.*;
import java.util.*;
public class Main
{
public static void main (String[] args) throws java.lang.Exception
{
Scanner in = new Scanner(System.in);
while(in.hasNextLine()) {
String s = in.nextLine();
StringBuilder sb = new StringBuilder(s);
sb.reverse();
char x[] = s.toCharArray();
char y[] = sb.toString().toCharArray();
sb = getStringsLCS(x,y);
System.out.println(s.length() - sb.length());
}
}
public static StringBuilder getStringsLCS(char []x, char[] y) {
int m = x.length;
int n = y.length;
int [][] c = new int[m + 1][n + 1];
int [][] b = new int[m + 1][n + 1];
for(int i = 0;i <= m; i++) {
c[i][0] = 0;
}
for(int i = 0;i <= n; i++) {
c[0][i] = 0;
}
for(int i = 0;i < m; i++) {
for(int j = 0;j < n; j++) {
if(x[i] == y[j]) {
c[i + 1][j + 1] = c[i][j] + 1;
b[i + 1][j + 1] = 0;
}
else if(c[i + 1][j] >= c[i][j + 1]) {
c[i + 1][j + 1] = c[i + 1][j];
b[i + 1][j + 1] = 1;
}
else {
c[i + 1][j + 1] = c[i][j + 1];
b[i + 1][j + 1] = 2;
}
}
}
//printArray2D(b);
return outputStringsLCS(b,x,m,n);
}
static void printArray2D(int[][] c) {
for(int i = 0;i < c.length;i ++) {
for(int j = 0;j < c[0].length;j ++) {
System.out.print(c[i][j]);
}
System.out.println("");
}
}
static StringBuilder outputStringsLCS(int[][] b,char[] x, int i, int j) {
if(i == 0 || j == 0) {
return new StringBuilder();
}
StringBuilder sb;
if(b[i][j] == 0) {
sb = outputStringsLCS(b, x, i - 1, j - 1);
sb.append(x[i - 1]);
}
else if(b[i][j] == 1) {
return outputStringsLCS(b, x, i, j - 1);
}
else {
return outputStringsLCS(b, x, i - 1, j);
}
return sb;
}
}