Codeforces 487B Strip(RMQ)

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题目链接：Codeforces 487B Strip

#include <cstdio>#include <cstring>#include <stack>#include <vector>#include <algorithm>using namespace std;const int maxn = 1e5 + 5;const int maxr = 20;const int inf = 0x3f3f3f3f;int ca, cd, AS[maxn], DS[maxn];int N, S, L, Db[maxn][maxr], Ds[maxn][maxr], dp[maxn];vector<int> Arr;void init(const vector<int>& arr) {int n = arr.size();for (int i = 1; i < n; i++)Db[i][0] = Ds[i][0] = arr[i];for (int j = 1; (1<<j) <= n; j++) {for (int i = 0; i + (1<<j) - 1 < n; i++) {Ds[i][j] = min(Ds[i][j-1], Ds[i+(1<<(j-1))][j-1]);Db[i][j] = max(Db[i][j-1], Db[i+(1<<(j-1))][j-1]);}}}int query(int l, int r) {int k = 0;while ((1<<(k+1)) <= r - l + 1)k++;return max(Db[l][k], Db[r-(1<<k)+1][k]) - min(Ds[l][k], Ds[r-(1<<k)+1][k]);}void solve() {memset(dp, inf, sizeof(dp));int mv = dp[0] = 0;for (int i = L; i <= N; i++) {while (i - mv >= L && (query(mv + 1, i) > S || dp[mv] == inf))mv++;if (i - mv >= L)dp[i] = min(dp[i], dp[mv] + 1);//printf("%d\n", dp[i]);}if (dp[N] == inf)dp[N] = -1;printf("%d\n", dp[N]);}int main () {int x;scanf("%d%d%d", &N, &S, &L);Arr.push_back(0);for (int i = 0; i < N; i++) {scanf("%d", &x);Arr.push_back(x);}init(Arr);solve();return 0;}

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