poj 1159 Palindrome

Palindrome

Time Limit: 3000MS		Memory Limit: 65536K
Total Submissions: 22525		Accepted: 7549

Description

A palindrome is a symmetrical string, that is, a string read identically from left to right as well as from right to left. You are to write a program which, given a string, determines the minimal number of characters to be inserted into the string in order to obtain a palindrome.

As an example, by inserting 2 characters, the string "Ab3bd" can be transformed into a palindrome ("dAb3bAd" or "Adb3bdA"). However, inserting fewer than 2 characters does not produce a palindrome.

Input

Your program is to read from standard input. The first line contains one integer: the length of the input string N, 3 <= N <= 5000. The second line contains one string with length N. The string is formed from uppercase letters from 'A' to 'Z', lowercase letters from 'a' to 'z' and digits from '0' to '9'. Uppercase and lowercase letters are to be considered distinct.

Output

Your program is to write to standard output. The first line contains one integer, which is the desired minimal number.

Sample Input

5
Ab3bd

Sample Output

2

Source

IOI 2000

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//5042643 11410 1159 Memory Limit Exceeded   C++ 541B 2009-04-25 10:46:03
//5042698 11410 1159 Accepted 40676K 1454MS C++ 543B 2009-04-25 10:52:06
#include <iostream>
#define MAX 5002
using namespace std;
char str[MAX];
short dp[MAX][MAX];  //第一次用这种类型
int len;
int GetMin(int a,int b)
{
 if(a>b)
  return b;
 else
  return a;
}
int main()
{
 int r,i,j;
 while(scanf("%d",&len)!=EOF)
 {
  scanf("%s",str+1);
  for(i=1;i<=len;i++)
   dp[i][i]=0;
  for(r=2;r<=len;r++)
   for(i=1;i<=len-r+1;i++)
   {
    j=i+r-1;
    if(str[j]==str[i])
     dp[i][j]=dp[i+1][j-1];
    else
     dp[i][j]=GetMin(dp[i+1][j]+1,dp[i][j-1]+1);
   }
  printf("%d\n",dp[1][len]);
 }
 return 0;
}