Submission #765212

#	Time	Username	Problem	Language	Result	Execution time	Memory
765212		yusuf12360	Watching (JOI13_watching)	C++14	0 / 100	3 ms	340 KiB

watching

#include<bits/stdc++.h>
using namespace std;
vector<int> a;
int n;
int binser(int x) {
	int l=0, r=n-1, ans;
	while(l<=r) {
		int mid=l+r>>1;
		if(a[mid]<x) ans=mid, l=mid+1;
		else r=mid-1;
	}
	return ans;
}
bool can(int w, int p, int q) {
	int idx=0;
	while(idx<n) {
		if(p>1 && q) {
			int BIG=binser(a[idx]+2*w);
			if(BIG==n-1) return 1;
			int SMALL=binser(a[idx]+w);
			if(SMALL==n-1) return 1;
			SMALL=binser(a[SMALL+1]+w);
			if(SMALL==n-1) return 1;
			if(SMALL>BIG) p-=2, idx=SMALL;
			else q--, idx=BIG;
		} else if(p && q) {
			int BIG=binser(a[idx]+2*w), SMALL=binser(a[idx]+w);
			if(BIG==n-1 || SMALL==n-1) return 1;
			if(BIG==SMALL) p--, idx=SMALL;
			else q--, idx=BIG;
		} else if(p) idx=binser(a[idx]+w), p--;
		else if(q) idx=binser(a[idx]+2*w), q--;
		else return 0;
		idx++;
	}
	return 1;
}
int main() {
	ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
	int p, q; cin >> n >> p >> q;
	a.resize(n);
	for(int &p : a) cin >> p;
	sort(a.begin(), a.end());
	int l=1, r=1e9, w=1e9;
	while(l<=r) {
		int mid=l+r>>1;
		if(can(mid, p, q)) w=mid, r=mid-1;
		else l=mid+1;
	}
	cout << w << '\n';
	return 0;
}

Compilation message (stderr)

watching.cpp: In function 'int binser(int)':
watching.cpp:8:12: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
    8 |   int mid=l+r>>1;
      |           ~^~
watching.cpp: In function 'int main()':
watching.cpp:46:12: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   46 |   int mid=l+r>>1;
      |           ~^~
watching.cpp: In function 'int binser(int)':
watching.cpp:12:9: warning: 'ans' may be used uninitialized in this function [-Wmaybe-uninitialized]
   12 |  return ans;
      |         ^~~
watching.cpp: In function 'bool can(int, int, int)':
watching.cpp:34:6: warning: 'ans' may be used uninitialized in this function [-Wmaybe-uninitialized]
   34 |   idx++;
      |   ~~~^~
watching.cpp:29:4: warning: 'ans' may be used uninitialized in this function [-Wmaybe-uninitialized]
   29 |    if(BIG==SMALL) p--, idx=SMALL;
      |    ^~
watching.cpp:29:4: warning: 'ans' may be used uninitialized in this function [-Wmaybe-uninitialized]
watching.cpp:24:4: warning: 'ans' may be used uninitialized in this function [-Wmaybe-uninitialized]
   24 |    if(SMALL>BIG) p-=2, idx=SMALL;
      |    ^~
watching.cpp:22:24: warning: 'ans' may be used uninitialized in this function [-Wmaybe-uninitialized]
   22 |    SMALL=binser(a[SMALL+1]+w);
      |                   ~~~~~^~
watching.cpp:24:4: warning: 'ans' may be used uninitialized in this function [-Wmaybe-uninitialized]
   24 |    if(SMALL>BIG) p-=2, idx=SMALL;
      |    ^~

• Subtask 1: 0 / 50
• Subtask 2: 0 / 50