codeforces 558E A Simple Task 线段树

题目链接

题意较为简单。

思路：

因为只有26个字母，所以用26棵线段树维护就好了，比较容易。

#include <iostream>#include <string>#include <vector>#include <cstring>#include <cstdio>#include <map>#include <queue>#include <algorithm>#include <stack>#include <cstring>#include <cmath>#include <set>#include <vector>using namespace std;template <class T>inline bool rd(T &ret) {char c; int sgn;if (c = getchar(), c == EOF) return 0;while (c != '-' && (c<'0' || c>'9')) c = getchar();sgn = (c == '-') ? -1 : 1;ret = (c == '-') ? 0 : (c - '0');while (c = getchar(), c >= '0'&&c <= '9') ret = ret * 10 + (c - '0');ret *= sgn;return 1;}template <class T>inline void pt(T x) {if (x <0) {putchar('-');x = -x;}if (x>9) pt(x / 10);putchar(x % 10 + '0');}typedef long long ll;typedef pair<ll, ll> pii;const int N = 1e5 + 100;#define lson (id<<1)#define rson (id<<1|1)#define L(x) tree[x].l#define R(x) tree[x].r#define Hav(x) tree[x].hav#define Siz(x) tree[x].siz#define Lazy(x) tree[x].lazystruct Tree {struct Node {int l, r, siz;//siz表示区间长度int hav;//hav表示这个区间的和 int lazy;//lazy为2表示清空区间 lazy为1表示把区间都变为1}tree[N << 2];void build(int l, int r, int id) {L(id) = l; R(id) = r; Siz(id) = r - l + 1;Hav(id) = Lazy(id) = 0;if (l == r)return;int mid = (l + r) >> 1;build(l, mid, lson); build(mid + 1, r, rson);}void Down(int id) {if (Lazy(id) == 1) {Lazy(id) = 0;Hav(lson) = Siz(lson); Hav(rson) = Siz(rson);Lazy(lson) = Lazy(rson) = 1;}else if (Lazy(id) == 2) {Lazy(id) = 0;Hav(lson) = Hav(rson) = 0;Lazy(lson) = Lazy(rson) = 2;}}void Up(int id) {Hav(id) = Hav(lson) + Hav(rson);}void updata(int l, int r, int val, int id) {if (l == L(id) && R(id) == r) {if (val == 1) Hav(id) = Siz(id);else Hav(id) = 0;Lazy(id) = val;return;}Down(id);int mid = (L(id) + R(id)) >> 1;if (r <= mid)updata(l, r, val, lson);else if (mid < l)updata(l, r, val, rson);else {updata(l, mid, val, lson);updata(mid + 1, r, val, rson);}Up(id);}int query(int l, int r, int id) {if (l == L(id) && R(id) == r) {return Hav(id);}Down(id);int mid = (L(id) + R(id)) >> 1, ans = 0;if (r <= mid)ans = query(l, r, lson);else if (mid < l)ans = query(l, r, rson);else {ans = query(l, mid, lson) + query(mid + 1, r, rson);}Up(id);return ans;}};Tree alph[26];int n, q;char s[N];int sum[26];int main() {rd(n); rd(q);for (int i = 0; i < 26; i++)alph[i].build(1, n, 1);scanf("%s", s + 1);for (int i = 1; i <= n; i++) {alph[s[i] - 'a'].updata(i, i, 1, 1);}while (q--) {int l, r, in;rd(l); rd(r); rd(in);memset(sum, 0, sizeof sum);for (int i = 0; i < 26; i++){sum[i] += alph[i].query(l, r, 1);alph[i].updata(l, r, 2, 1);}int tim = 26, i;if (in)i = 0; else i = 25, in = -1;for (;tim--; i += in) {if (sum[i] == 0)continue;alph[i].updata(l, l + sum[i] - 1, 1, 1);l += sum[i];}}for (int i = 1; i <= n; i++){for (int j = 0; j < 26; j++)if (alph[j].query(i, i, 1)){putchar(j + 'a'); break;}}return 0;}