uva 12002 - Happy Birthday(LIS)

来源：互联网发布：.shop域名价值编辑：程序博客网时间：2024/05/17 07:21

题目链接：uva 12002 - Happy Birthday

题目大意：给出一个序列，表示说有n个碟子，每个数字代表碟子的大小，现在开始堆碟子，可以选择在上面和下面放，不过放上面的碟子必须小于等于最上面的碟子，放在下面的碟子必须大于等于最下面的碟子。问说最多能放多少碟子。

解题思路：和uva 11456 做法相似，只不过说这题可以取相同的大小，那么只需要分成两种情况考虑即可，一种是将当前起始的值归入升序中，一种是归进降序中。

#include <stdio.h>#include <string.h>#include <algorithm>using namespace std;const int N = 505;int n, s[N], up[N], down[N];void init () {for (int i = 1; i <= n; i++)scanf("%d", &s[i]);for (int i = n; i; i--) {up[i] = down[i] = 1;for (int j = n; j > i; j--) {if (s[j] <= s[i])down[i] = max(down[i], down[j] + 1);if (s[j] >= s[i])up[i] = max(up[i], up[j] + 1);}}}int cat (int k, int p, int a) {int ans = 0;for (int i = p; i <= n; i++) {if (a == 1 && s[i] >= k)ans = max(ans, up[i]);if (a == -1 && s[i] <= k)ans = max(ans, down[i]);}return ans;}int solve () {int ans = 0;for (int i = 1; i <= n; i++) {int u = up[i] + cat(s[i]-1, i, -1);int v = down[i] + cat(s[i]+1, i, 1);ans = max(ans, max(u, v));}return ans;}int main () {while (scanf("%d", &n) == 1 && n) {init ();printf("%d\n", solve());}return 0;}

1 0