区间DP + 线性DP

#include <bits/stdc++.h>
using namespace std;
const int maxn = 505;

int n, a[maxn], f[maxn][maxn], g[maxn];

int main() {
    cin >> n;
    for (int i = 1; i <= n; i++)
        cin >> a[i];
    for (int l = 1; l <= n; l++) {
        for (int i = 1; i+l-1 <= n; i++) {
            int j = i+l-1;
            if (l == 1) f[i][j] = a[i];
            else {
                for (int k = i; k < j; k++) {
                    if (f[i][k] == f[k+1][j] && f[i][k] > 0) {
                        f[i][j] = f[i][k] + 1;
                        break;
                    }
                }
            }
        }
    }
    for (int i = 1; i <= n; i++) {
        g[i] = i;
        for (int j = 1; j <= i; j++)
            if (f[j][i])
                g[i] = min(g[i], g[j-1] + 1);
    }
    cout << g[n] << endl;
    return 0;
}