传送门

f[i][j]表示区间 i-j 合并的最大值

转移：

若f[i][k] && f[k+1][j] && f[i][k] == f[k+1][j] –> f[i][j] = max(f[i][k]+1,f[i][j])

但要注意， 若f[i][k]!=f[k+1][j]，那么无法进行转移

代码

#include <cstdio>
#include <iostream>
#define max(x, y) ((x) > (y) ? (x) : (y))int n, ans;
int f[5001][5001];inline int read()
{
int x = 0, f = 1;
char ch = getchar();
for(; !isdigit(ch); ch = getchar()) if(ch == '-') f = -1;
for(; isdigit(ch); ch = getchar()) x = (x << 1) + (x << 3) + ch - '0';
return x * f;
}int main()
{
int i, j, k;
n = read();
for(i = 1; i <= n; i++) f[i][i] = read(), ans = max(ans, f[i][i]);
for(i = n - 1; i >= 1; i--)
for(j = i + 1; j <= n; j++)
{
for(k = i; k < j; k++)
if(f[i][k] && f[k + 1][j] && f[i][k] == f[k + 1][j])
f[i][j] = max(f[i][j], f[i][k] + 1);
ans = max(ans, f[i][j]);
}
printf("%d\n", ans);
return 0;
}