BZOJ1260(CQOI2007)[涂色paint]--区间DP

【链接】
bzoj1260

【解题报告】

裸的区间DP

定义 f[color][i][j] 区间 [i,j] 颜色为 color 的最优解

#include
#include
#include
using namespace std;
const int maxn=55;
int n,a[maxn],f[30][maxn][maxn];
inline char nc()
{
    static char buf[100000],*l,*r;
    if (l==r) r=(l=buf)+fread(buf,1,100000,stdin);
    if (l==r) return EOF; return *l++;
}
inline int Read()
{
    int res=0,f=1; char ch=nc(),cc=ch;
    while (ch<'0'||ch>'9') cc=ch,ch=nc();
    if (cc=='-') f=-1;
    while (ch>='0'&&ch<='9') res=res*10+ch-48,ch=nc();
    return res*f;
}
int Dfs(int color,int L,int R)
{
    while (a[L]==color&&L<=R) L++;
    while (a[R]==color&&L<=R) R--;
    if (L>R) return 0;
    if (f[color][L][R]>0) return f[color][L][R];
    f[color][L][R]=R-L;
    for (int k=L; k<=R; k++)
     f[color][L][R]=min(f[color][L][R],Dfs(a[L],L,k)+Dfs(color,k+1,R));++f[color][L][R];
    return f[color][L][R];
}
int main()
{
    freopen("1260.in","r",stdin);
    freopen("1260.out","w",stdout);
    char ch=getchar(); n=0;
    while (ch>='A'&&ch<='Z') a[++n]=ch-64,ch=getchar();
    memset(f,255,sizeof(f));
    for (int i=1; i<=n; i++) f[a[i]][i][i]=1;
    printf("%d",Dfs(0,1,n));
    return 0;
}