1100: [POI2007]对称轴osi

将2相邻相同颜色的缩成1个，然后状压dp。

#include<iostream>#include<cstdio>#include<cstring>#include<algorithm>using namespace std;int n,a[505],num[505],f[505][505],x,y,cnt;int main(){    scanf("%d",&n);    for(int i=1;i<=n;i++)    {        y=x;        scanf("%d",&x);        if(x!=y||i==1) a[++cnt]=x,num[cnt]=1;        else num[cnt]++;    }    memset(f,127/3,sizeof(f));    n=cnt;    for(int i=1;i<=n;i++)    f[i][i]= num[i] == 1 ? 2:1;    for(int len=2;len<=n;len++)    {        for(int i=1;i+len-1<=n;i++)        {            int j=i+len-1;            for(int k=i;k<j;k++)            {                f[i][j]=min(f[i][j],f[i][k]+f[k+1][j]);            }            if(a[i]==a[j])            {                if(num[i]+num[j]>=3) f[i][j]=min(f[i][j],f[i+1][j-1]);                else f[i][j]=min(f[i][j],f[i+1][j-1]+1);            }        }    }    printf("%d\n",f[1][n]);}