#6285. 数列分块入门 9

https://loj.ac/s/1466637

LibreOJ/6285/6285.cpp

@@ -0,0 +1,106 @@
+#include <algorithm>
+#include <cmath>
+#include <cstring>
+#include <iostream>
+#include <vector>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 100005;
+
+int n, t, a[N], st[N], ed[N], pos[N], f[1005][1005], cnt[N];
+std::vector<int> nums, v[N];
+
+inline int find(int x) {
+    return std::lower_bound(nums.begin(), nums.end(), x) - nums.begin();
+}
+
+void pre(int x) {
+    memset(cnt, 0x00, sizeof(cnt));
+    std::pair<int, int> res;
+
+    for (int i = st[x]; i <= n; i++) {
+        cnt[a[i]]++;
+
+        if (cnt[a[i]] > res.first || (cnt[a[i]] == res.first && nums[a[i]] < nums[res.second])) {
+            res = std::make_pair(cnt[a[i]], a[i]);
+        }
+
+        f[x][pos[i]] = res.second;
+    }
+}
+
+inline int get(int x, int l, int r) {
+    return std::upper_bound(v[x].begin(), v[x].end(), r) - std::lower_bound(v[x].begin(), v[x].end(), l);
+}
+
+int query(int l, int r) {
+    int p = pos[l],
+        q = pos[r];
+    std::pair<int, int> res;
+
+    if (p == q) {
+        for (int i = l; i <= r; i++) {
+            int _ = get(a[i], l, r);
+            if (_ > res.first || (_ == res.first && nums[a[i]] < nums[res.second])) {
+                res = std::make_pair(_, a[i]);
+            }
+        }
+
+        return nums[res.second];
+    }
+
+    res.second = f[p + 1][q - 1];
+    res.first = get(res.second, l, r);
+
+    for (int i = l; i <= ed[p]; i++) {
+        int _ = get(a[i], l, r);
+        if (_ > res.first || (_ == res.first && nums[a[i]] < nums[res.second])) {
+            res = std::make_pair(_, a[i]);
+        }
+    }
+    for (int i = st[q]; i <= r; i++) {
+        int _ = get(a[i], l, r);
+        if (_ > res.first || (_ == res.first && nums[a[i]] < nums[res.second])) {
+            res = std::make_pair(_, a[i]);
+        }
+    }
+
+    return nums[res.second];
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+
+    cin >> n;
+
+    t = std::sqrt(n);
+
+    for (int i = 1; i <= n; i++) {
+        cin >> a[i];
+        pos[i] = (i - 1) / t + 1;
+        nums.push_back(a[i]);
+    }
+
+    std::sort(nums.begin(), nums.end());
+    nums.erase(std::unique(nums.begin(), nums.end()), nums.end());
+    nums.insert(nums.begin(), 0);
+
+    for (int i = 1; i <= n; i++) v[a[i] = find(a[i])].push_back(i);
+
+    for (int i = 1; i <= pos[n]; i++) {
+        st[i] = (i - 1) * t + 1;
+        ed[i] = std::min(n, i * t);
+    }
+
+    for (int i = 1; i <= pos[n]; i++) pre(i);
+
+    for (int i = 1, l, r; i <= n; i++) {
+        cin >> l >> r;
+        cout << query(l, r) << endl;
+    }
+
+    return 0;
+}