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codeforces#FF(div2) DZY Loves Sequences
n个数,可以任意改变其中一个数,求最长的上升子区间长度
思路:记录一个from[i]表示从位置i的数开始最长的上升区间长度
记录一个to[i]表示到位置i的数所能达到的最长上升区间长度
枚举要改变的数的位置i,此时能达到的长度为to[i - 1] + from[i + 1] + 1,取最大值
//#pragma comment(linker, "/STACK:102400000,102400000") //HEAD #include <cstdio> #include <cstring> #include <vector> #include <iostream> #include <algorithm> #include <queue> #include <string> #include <set> #include <stack> #include <map> #include <cmath> #include <cstdlib> using namespace std; //LOOP #define FE(i, a, b) for(int i = (a); i <= (b); ++i) #define FED(i, b, a) for(int i = (b); i>= (a); --i) #define REP(i, N) for(int i = 0; i < (N); ++i) #define CLR(A,value) memset(A,value,sizeof(A)) //STL #define PB push_back //INPUT #define RI(n) scanf("%d", &n) #define RII(n, m) scanf("%d%d", &n, &m) #define RIII(n, m, k) scanf("%d%d%d", &n, &m, &k) #define RS(s) scanf("%s", s) typedef long long LL; const int INF = 0x3f3f3f3f; const int MAXN = 1010; #define FF(i, a, b) for(int i = (a); i < (b); ++i) #define FD(i, b, a) for(int i = (b) - 1; i >= (a); --i) #define CPY(a, b) memcpy(a, b, sizeof(a)) #define FC(it, c) for(__typeof((c).begin()) it = (c).begin(); it != (c).end(); it++) #define EQ(a, b) (fabs((a) - (b)) <= 1e-10) #define ALL(c) (c).begin(), (c).end() #define SZ(V) (int)V.size() #define RIV(n, m, k, p) scanf("%d%d%d%d", &n, &m, &k, &p) #define RV(n, m, k, p, q) scanf("%d%d%d%d%d", &n, &m, &k, &p, &q) #define WI(n) printf("%d\n", n) #define WS(s) printf("%s\n", s) typedef vector <int> VI; typedef unsigned long long ULL; const double eps = 1e-10; const LL MOD = 1e9 + 7; int a[100010]; int to[100010], from[100010]; int main() { //freopen("0.txt", "r", stdin); int n; while (~RI(n)) { FE(i, 1, n) RI(a[i]), to[i] = from[i] = 1; FE(i, 2, n) if (a[i] > a[i - 1]) to[i] = to[i - 1] + 1; FED(i, n - 1, 1) if (a[i + 1] > a[i]) from[i] = from[i + 1] + 1; // FE(i, 1, n) // cout << to[i] <<' ';;cout << endl; // FE(i, 1, n) // cout << from[i] <<' ' ; cout << endl; int ans = 1; if (n > 1) ans = max(from[2] + 1, to[n - 1] + 1); FE(i, 2, n - 1) { if (a[i + 1] - a[i - 1] >= 2) { if (to[i - 1] + from[i + 1] + 1 > ans) { ans = to[i - 1] + from[i + 1] + 1; // cout << i <<endl; } } else { ans = max(ans, to[i - 1] +1); ans = max(ans, from[i + 1] + 1); } } cout << ans << endl; } return 0; }
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