Codeforces 899F Letters Removing

Codeforces 899F Letters Removing

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <algorithm>
#include <queue>
#include <vector>
#include <stack>
#include <map>
#include <set>
#include <cmath>
#include <cctype>
#include <ctime>
#include <bitset>

using namespace std;

typedef long long ll;
typedef pair<int, int> pii;
const int maxn = 2e5 + 10;
char str[maxn];
int n, m, cnt = 0;
int k[1000], last[maxn], pre[maxn], c[maxn];
set<int> s[100];
set<int>::iterator itr;
bool vis[maxn];

int lowbit(int x) { return x & (-x); }
void update(int x) { while (x < maxn) { ++c[x]; x += lowbit(x); } }
int query(int x) {
    int ret = 0;
    while (x > 0) { ret += c[x]; x -= lowbit(x); }
    return ret;
}
int cal(int x) {
    int low = 1, high = n + 1, mid;
    while (low < high) {
        mid = (low + high) / 2;
        if (mid - query(mid) >= x) { high = mid; } else { low = mid + 1; }
    }
    return high;
}
void remove(int l, int r, int x) {
    if (s[x].empty() || *(--s[x].end()) < l) { return; }
//    printf("%d %d
", l, r);
    int t = *s[x].lower_bound(l);
    while (t <= r) {
//        printf("t = %d
", t);
        s[x].erase(t); update(t); last[pre[t]] = last[t];
        pre[last[t]] = pre[t]; t = last[t];
    }
}
void print() {
    memset(vis, false, sizeof(vis));
    for (int i = 0; i < cnt; ++i) {
        for (itr = s[i].begin(); itr != s[i].end(); ++itr) { vis[*itr] = true; }
    }
    for (int i = 1; i <= n; ++i) {
        if (vis[i]) { printf("%c", str[i - 1]); }
    }
    printf("
");
}

int main() {
#ifdef __AiR_H
    freopen("F.in", "r", stdin);
//    freopen("out.txt", "w", stdout);
#endif // __AiR_H
    scanf("%d %d %s", &n, &m, str); int l, r, t, t1, l_t, r_t; char c;
    for (int i = 'a'; i <= 'z'; ++i) { k[i] = cnt++; }
    for (int i = 'A'; i <= 'Z'; ++i) { k[i] = cnt++; }
    for (int i = '0'; i <= '9'; ++i) { k[i] = cnt++; }
    for (int i = 1; i <= n; ++i) {
        t = k[str[i - 1]];
        if (s[t].empty()) { s[t].insert(i); continue; }
        t1 = *(--s[t].end()); pre[i] = t1; last[t1] = i; s[t].insert(i);
    }
    for (int i = 0; i < cnt; ++i) {
        if (s[i].empty()) { continue; }
        last[*(--s[i].end())] = n + 1;
    }
    while (m--) {
        scanf("%d %d %c", &l, &r, &c);
        l_t = cal(l); r_t = cal(r); t = k[c]; remove(l_t, r_t, t);
    }
    print();
    return 0;
}