POJ 1159 Palindrome

#include<cstdio>
#include<cstring>
#include<cstdlib>
#define MAXN 5005
#define max(a, b) ( a > b ? a : b)
short f[MAXN][MAXN], len;
char a[MAXN], b[MAXN];

void rev()
{
for( int i = len, j = 1; i >= 1; i --, j ++)
{
b[j] = a[i];
}
}

void dp()
{
memset( f, 0, sizeof f);
for( int i = 1; i <= len; i ++)
for( int j = 1; j <= len; j ++)
{
if( a[i] == b[j])
f[i][j] = f[i - 1][j - 1] + 1;
else
f[i][j] = max( f[i - 1][j], f[i][j - 1]);
}
}

int main()
{
while( scanf( "%d", &len) != EOF)
{
scanf( "%s", a + 1);
rev();
dp();
printf( "%d\n", len - f[len][len]);
}
return 0;
}

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
const int MAXN = 5005;
int dp[MAXN], prei, prej, len;
char a[MAXN];
int max(int a, int b)
{return a > b ? a : b;}
int main()
{
int i, j;
while(scanf("%d", &len) != EOF)
{
memset(dp, 0, sizeof(dp));
scanf("%s", a);
prej = prei = 0;
for(i = 0; i < len; ++ i)
{
prej = 0;
for(j = 0; j < len; ++ j)
{
prei = dp[j + 1];
if(a[i] == a[len - j - 1])
dp[j + 1] = prej + 1;
else
dp[j + 1] = max(dp[j + 1], dp[j]);
prej = prei;
}
}
printf("%d\n", len - dp[len]);
}
return 0;
}