Submission #853146

#	Time	Username	Problem	Language	Result	Execution time	Memory
853146		qin	Shortcut (IOI16_shortcut)	C++17	0 / 100	1 ms	600 KiB

shortcut

#include <bits/stdc++.h>
#define fi first
#define se second
#define ssize(x) int(x.size())
#define pn printf("\n");
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<int, ll> pil;
typedef pair<ll, int> pli;
typedef pair<ll, ll> pll;
int inf = 1e09; ll infll = 1e18;
struct gr{
		vector<vector<pil>> g;
		vector<ll> dist;
		void init(int n){ g.resize(n), dist.resize(n); }
		void prepare(){ fill(dist.begin(), dist.end(), infll); }
		void dfs(int x, ll d){
				dist[x] = d;
				for(pil u : g[x]) if(d+u.se < dist[u.fi]) dfs(u.fi, d+u.se);
		}
} gr;
ll find_diam(int n, int a, int b, int c){
		gr.g[a].emplace_back(b, c), gr.g[b].emplace_back(a, c);
		ll tmp_res = 0;
		for(int u = 0; u < n<<1; ++u){
				gr.prepare(); gr.dfs(u, 0);
				ll d = -1;
				for(int i = 0; i < n<<1; ++i) if(gr.dist[i] != infll && d < gr.dist[i]) d = gr.dist[i];
				tmp_res = max(tmp_res, d);
		}
		gr.g[a].pop_back(), gr.g[b].pop_back();
		return tmp_res;
}
ll find_shortcut(int n, vector<int> d_main, vector<int> d_sec, int C){
		gr.init(n<<1);
		for(int i = 0; i < n-1; ++i) gr.g[i].emplace_back(i+1, d_main[i]), gr.g[i+1].emplace_back(i, d_main[i]);
		for(int i = 0; i < n; ++i) gr.g[i].emplace_back(i+n, d_sec[i]), gr.g[i+n].emplace_back(i, d_sec[i]);
		ll result = infll;
		vector<int> candidates;
		for(int p = 0; p < n-1; ++p){
				int l = p+1, r = n-1;
				//printf("%d:\n", p);
				while(r-l >= 4){
						//printf("%d %d: ", l, r);
						int a = l+(r-l)/4, b = l+2*(r-l)/4, c = l+3*(r-l)/4;
						ll res_a = find_diam(n, p, a, C), res_b = find_diam(n, p, b, C), res_c = find_diam(n, p, c, C);
						//printf("%d %d %d, %lld %lld %lld\n", a, b, c, res_a, res_b, res_c);
						if(res_a < res_b && res_b <= res_c) r = c;
						else if(res_a < res_b && res_b < res_c) r = b;
						else if(res_a <= res_b && res_b < res_c) r = c;
						else if(res_a > res_b && res_b >= res_c) l = a;
						else if(res_a > res_b && res_b > res_c) l = b;
						else if(res_a >= res_b && res_b > res_c) l = a;
						else{
								res_a = find_diam(n, p, l+1, C), res_b = find_diam(n, p, r-1, C);
								if(res_a < res_b) r = a;
								else if(res_a > res_b) l = c;
								else ++l;
						}
				} //printf("%d %d\n", l, r);
				for(int i = l; i <= r; ++i) result = min(result, find_diam(n, p, i, C));
		}
				
		return result;
}
#ifdef LOCAL
int main(){
		int n, c; scanf("%d%d", &n, &c);
		vector<int> d_main(n), d_sec(n);
		for(int i = 0; i < n-1; ++i) scanf("%d", &d_main[i]);
		for(int i = 0; i < n; ++i) scanf("%d", &d_sec[i]);
		ll result = find_shortcut(n, d_main, d_sec, c);
		printf("%lld\n", result);
		return 0;
}
#endif

• Subtask 1: 0 / 9
• Subtask 2: 0 / 14
• Subtask 3: 0 / 8
• Subtask 4: 0 / 7
• Subtask 5: 0 / 33
• Subtask 6: 0 / 22
• Subtask 7: 0 / 4
• Subtask 8: 0 / 3