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https://git.sb/baoshuo/OI-codes.git
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86 lines
1.6 KiB
C++
86 lines
1.6 KiB
C++
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#include <iostream>
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#include <algorithm>
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#include <cmath>
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#include <string>
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#include <tuple>
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#include <vector>
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using std::cin;
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using std::cout;
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const char endl = '\n';
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const int N = 6e4 + 5;
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int n, m, t, a[N], cnt[1 << 26], res, ans[N];
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std::string s;
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std::vector<std::tuple<int, int, int>> qs;
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void add(int x) {
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res += cnt[a[x]]++;
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for (int i = 0; i < 26; i++) {
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res += cnt[a[x] ^ (1 << i)];
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}
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}
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void del(int x) {
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res -= --cnt[a[x]];
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for (int i = 0; i < 26; i++) {
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res -= cnt[a[x] ^ (1 << i)];
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}
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}
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int main() {
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std::ios::sync_with_stdio(false);
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cin.tie(nullptr);
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cin >> n >> m >> s;
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s = ' ' + s;
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for (int i = 1; i <= n; i++) {
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a[i + 1] = a[i] ^ (1 << (s[i] - 'a'));
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}
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for (int i = 1, l, r; i <= m; i++) {
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cin >> l >> r;
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qs.emplace_back(i, l, r + 1);
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}
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t = std::sqrt(n + 1);
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std::sort(qs.begin(), qs.end(), [&](std::tuple<int, int, int> lhs, std::tuple<int, int, int> rhs) -> bool {
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int p = std::get<1>(lhs) / t,
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q = std::get<1>(rhs) / t;
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int x = std::get<2>(lhs),
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y = std::get<2>(rhs);
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return p == q
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? p & 1 ? x < y : x > y
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: p < q;
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});
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int i = 0, j = 1;
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for (auto q : qs) {
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int id, l, r;
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std::tie(id, l, r) = q;
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while (i < r) add(++i);
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while (i > r) del(i--);
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while (j < l) del(j++);
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while (j > l) add(--j);
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ans[id] = res;
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}
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for (int i = 1; i <= m; i++) {
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cout << ans[i] << endl;
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}
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return 0;
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}
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