矩陣快速冪 CodeForces - 582B Once Again...

建出轉移矩陣...然後做矩陣快速冪就行了....

#include <bits/stdc++.h>
using namespace std;
typedef long long LL;

const int maxn = 105;
const int INF = 0x3f3f3f3f;

int mat[maxn][maxn];
int res[maxn][maxn];
int mid[maxn][maxn];
int a[maxn];
int n, m;

void calc(int b)
{
	memset(res, 0, sizeof res);
	while(b) {
		if(b % 2) {
			for(int i = 1; i <= n; i++)
				for(int j = 1; j <= n; j++) {
					mid[i][j] = -INF;
					for(int k = 1; k <= n; k++)
						mid[i][j] = max(mid[i][j], res[i][k] + mat[k][j]);
				}
			memcpy(res, mid, sizeof mid);
		}
		for(int i = 1; i <= n; i++)
			for(int j = 1; j <= n; j++) {
				mid[i][j] = -INF;
				for(int k = 1; k <= n; k++)
					mid[i][j] = max(mid[i][j], mat[i][k] + mat[k][j]);
			}
		memcpy(mat, mid, sizeof mid);
		b /= 2;
	}
}

void work()
{
	scanf("%d%d", &n, &m);
	
	for(int i = 1; i <= n; i++) scanf("%d", &a[i]);
	
	for(int i = 1; i <= n; i++)
		for(int j = 1; j <= n; j++)
			mat[i][j] = 0;
	
	for(int i = 1; i <= n; i++)
		for(int j = 1; j <= n; j++) {
			if(a[i] <= a[j]) {
				mat[i][j] = 1;
				for(int k = 1; k < j; k++)
					if(a[k] <= a[j])
						mat[i][j] = max(mat[i][j], mat[i][k] + 1);
			}
			else mat[i][j] = -INF;
		}
	calc(m);
	
	int ans = 0;
	for(int i = 1; i <= n; i++)
		for(int j = 1; j <= n; j++)
			ans = max(ans, res[i][j]);
	printf("%d\n", ans);
}

int main()
{
//freopen("data", "r", stdin);
	work();
	
	return 0;
}