BZOJ 1068: [SCOI2007]压缩 | 区间DP

题目:

http://www.lydsy.com/JudgeOnline/problem.php?id=1068

---

题解:

鸽

#include<cstdio>
#include<algorithm>
#include<cstring>
#include<cmath>
#define N 54
using namespace std;
int n,f[N][N][2];
char s[N];
inline bool check(int i,int j,int k)
{
    for (int l=0;l<k;l++)
    if (s[i+l]!=s[j+l]) return 0;
    return 1;
}
inline void upt(int &x,const int &y)
{
    if (x>y) x=y;
}
int main()
{
    scanf("%s",s+1);
    n=strlen(s+1);
    memset(f,127/3,sizeof(f));
    for (int i=1;i<=n;i++) f[i][i][0]=f[i][i][1]=1;
    for (int l=1;l<=n;l++)
    for (int i=1;i<=n;i++)
    {
        int j=i+l;
        if (j>n) break;
        upt(f[i][j][0],l+1);
        upt(f[i][j][1],l+1);
        for (int k=i;k<j;k++)
        {
        upt(f[i][j][0],f[i][k][0]+j-k);
        upt(f[i][j][1],f[i][k][1]+j-k);
        upt(f[i][j][1],f[i][k][1]+f[k+1][j][1]+1);
        }
        if (l&1)
        {
        int k=i+j>>1,t=l+1>>1;
        if (check(i,k+1,t))
            upt(f[i][j][1],f[i][k][0]+1),upt(f[i][j][0],f[i][k][0]+1);
        }
    }
    printf("%d\n",min(f[1][n][0],f[1][n][1]));
    return 0;
}