萌新求助区间dp (70pts WA)

#include<bits/stdc++.h>
#define ll long long
#define For(i,l,r) for(int i=l;i<=r;++i)
using namespace std;
const int N=55,Inf=0x7fffffff,Mod=998244353;
char cch;
int res,zf;
inline int rd()
{
	while((cch=getchar())<45);
	if(cch^45)res=cch^48,zf=1;
	else res=0,zf=-1;
	while((cch=getchar())>=48)res=(res*10)+(cch^48);
	return res*zf;
}
inline void print(int x)
{
	if(x>9) print(x/10);
	putchar(x%10+'0');
}

int n,len;
char a[N],b[N];
int f[N][N];

int main()
{
	//freopen("P4170.in","r",stdin);
	//freopen("P4170.out","w",stdout);
	memset(f,63,sizeof(f));
	scanf("%s",b+1);
	len=strlen(b+1);
	For(i,1,len) if(b[i]^b[i-1]) a[++n]=b[i],f[n][n]=1;
	For(len,2,n)
	{
		For(l,1,n-len+1)
		{
			int r=l+len-1;
			if(a[l]==a[r]) f[l][r]=f[l+1][r-1]+1;
			For(k,l,r-1) f[l][r]=min(f[l][r],f[l][k]+f[k+1][r]);
		}
	}
	cout<<f[1][n];
	return 0;
}