Submission #531541

#	Time	Username	Problem	Language	Result	Execution time	Memory
531541		colazcy	Palinilap (COI16_palinilap)	C++17	100 / 100	164 ms	24672 KiB

palinilap

#include <cstdio>
#include <cassert>
#include <cstring>
#include <utility>
#include <algorithm>
#define let const auto
#define rep(name,beg,end) for(auto lim_##name = end,name = beg;name <= lim_##name;name++)
#define per(name,beg,end) for(auto lim_##name = end,name = beg;name >= lim_##name;name--)
#define repn(lim) for(auto REPN_lIM = lim,REPN = 1;REPN <= REPN_lIM;REPN++)
#define debug(...) fprintf(stderr,__VA_ARGS__)
#define trace() debug("line : %d, Function : %s\n",__LINE__,__FUNCTION__)
using ll = long long;
constexpr int maxn = 1e5 +10;
constexpr int lowbit(const int x){return x & (-x);}
int n;
char buf[maxn];
template <int base,int mod>
struct Hash{
	static int add(const int a,const int b){return a + b >= mod ? a + b - mod : a + b;}
	static int sub(const int a,const int b){return a >= b ? a - b : a - b + mod;}
	static int mul(const int a,const int b){return 1ll * a * b % mod;}

	int pw[maxn],sum[maxn],sum_rev[maxn];
	void init(){
		pw[0] = 1;
		rep(i,1,n)pw[i] = mul(pw[i - 1],base);
		rep(i,1,n)sum[i] = add(mul(sum[i - 1],base),buf[i]);
		per(i,n,1)sum_rev[i] = add(mul(sum_rev[i + 1],base),buf[i]);
	}
	int query(const int l,const int r){
		return sub(sum[r],mul(sum[l - 1],pw[r - l + 1]));
	}
	int query_rev(const int l,const int r){
		return sub(sum_rev[l],mul(sum_rev[r + 1],pw[r - l + 1]));
	}
};

Hash<127,1000000000 + 7> ha;
Hash<131,1000000000 + 9> hb;

struct fenwick{
	ll f[maxn];
	void add(int pos,const ll v){
		while(pos <= n + 1){
			f[pos] += v;
			pos += lowbit(pos);
		}
	}
	ll query(int pos){
		ll res = 0;
		while(pos){
			res += f[pos];
			pos -= lowbit(pos);
		}
		return res;
	}
}fs,fsi;

ll delta[maxn][26];
void modify(const int l,const int r,const int beg,const int delta){
	if(l > r)return;
	fs.add(l,beg);
	fs.add(l + 1,delta - beg);
	fs.add(r + 1,-(r - l + 1) * delta - beg);
	fs.add(r + 2,(r - l) * delta + beg);

	fsi.add(l,1ll * l * beg);
	fsi.add(l + 1,1ll * (l + 1) * (delta - beg));
	fsi.add(r + 1,1ll * (r + 1) * (-(r - l + 1) * delta - beg));
	fsi.add(r + 2,1ll * (r + 2) * ((r - l) * delta + beg));
}
ll query(const int p){
	return 1ll * (p + 1) * fs.query(p) - fsi.query(p);
}
ll sum,mx;
int main(){
	// std::freopen("palinilap.in","r",stdin);
	// std::freopen("palinilap.out","w",stdout);
	
	std::scanf("%s",buf + 1);
	n = std::strlen(buf + 1);
	ha.init(); hb.init();
	rep(i,1,n){
		int l = 0,r = std::min(i - 1,n - i),ans = 0;
		while(l <= r){
			let mid = (l + r) >> 1;
			if(std::make_pair(ha.query_rev(i - mid,i),hb.query_rev(i - mid,i)) == std::make_pair(ha.query(i,i + mid),hb.query(i,i + mid)))ans = mid,l = mid + 1;
			else r = mid - 1;
		}
		sum += ans + 1;
		rep(c,0,25)
			if(c != buf[i] - 'a')
				delta[i][c] += ans + 1;
		modify(i - ans,i,1,1);
		modify(i + 1,i + ans,ans,-1);
		if(i - ans != 1 && i + ans != n){
			let t = ans;
			l = 0,r = std::min(i - t - 3,n - (i + t + 2)),ans = -1;
			while(l <= r){
				let mid = (l + r) >> 1;
				if(std::make_pair(ha.query_rev(i - t - 2 - mid,i - t - 2),hb.query_rev(i - t - 2 - mid,i - t - 2)) == std::make_pair(ha.query(i + t + 2,i + t + 2 + mid),hb.query(i + t + 2,i + t + 2 + mid)))ans = mid,l = mid + 1;
				else r = mid - 1;
			}
			delta[i - t - 1][buf[i + t + 1] - 'a'] += ans + 2;
			delta[i + t + 1][buf[i - t - 1] - 'a'] += ans + 2;
		}
	}
	rep(i,1,n - 1){
		if(buf[i] != buf[i + 1]){
			int l = 0,r = std::min(i - 2,n - i - 2),ans = -1;
			while(l <= r){
				let mid = (l + r) >> 1;
				if(std::make_pair(ha.query_rev(i - 1 - mid,i - 1),hb.query_rev(i - 1 - mid,i - 1)) == std::make_pair(ha.query(i + 2,i + 2 + mid),hb.query(i + 2,i + 2 + mid)))ans = mid,l = mid + 1;
				else r = mid - 1;
			}
			delta[i][buf[i + 1] - 'a'] += ans + 2;
			delta[i + 1][buf[i] - 'a'] += ans + 2;
			continue;
		}
		int l = 0,r = std::min(i - 1,n - i - 1),ans = 0;
		while(l <= r){
			let mid = (l + r) >> 1;
			if(std::make_pair(ha.query_rev(i - mid,i),hb.query_rev(i - mid,i)) == std::make_pair(ha.query(i + 1,i + 1 + mid),hb.query(i + 1,i + 1 + mid)))ans = mid,l = mid + 1;
			else r = mid - 1;
		}
		sum += ans + 1;
		modify(i - ans,i,1,1);
		modify(i + 1,i + 1 + ans,ans + 1,-1);
		if(i - ans != 1 && i + 1 + ans != n){
			let t = ans;
			l = 0,r = std::min(i - ans - 3,n - (i + ans + 3)),ans = -1;
			while(l <= r){
				let mid = (l + r) >> 1;
				if(std::make_pair(ha.query_rev(i - t - 2 - mid,i - t - 2),hb.query_rev(i - t - 2 - mid,i - t - 2)) == std::make_pair(ha.query(i + t + 3,i + t + 3 + mid),hb.query(i + t + 3,i + t + 3 + mid)))ans = mid,l = mid + 1;
				else r = mid - 1;
			}
			delta[i - t - 1][buf[i + t + 2] - 'a'] += ans + 2;
			delta[i + t + 2][buf[i - t - 1] - 'a'] += ans + 2;
		}
	}
	rep(i,1,n)
		rep(c,0,25)
			if(c != buf[i] - 'a')
				mx = std::max(mx,delta[i][c] - query(i));
	std::printf("%lld\n",sum + mx);
	std::fclose(stdin);
	std::fclose(stdout);
	return 0;
}

Compilation message (stderr)

palinilap.cpp: In function 'int main()':
palinilap.cpp:80:12: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   80 |  std::scanf("%s",buf + 1);
      |  ~~~~~~~~~~^~~~~~~~~~~~~~

• Subtask 1: 17 / 17
• Subtask 2: 37 / 37
• Subtask 3: 46 / 46