codeforces 766B Mahmoud and a Triangle
B. Mahmoud and a Triangle
time limit per test
2 seconds
memory limit per test
256 megabytes
input
standard input
output
standard output
Mahmoud has n line segments, the i-th of them has length a**i. Ehab challenged him to use exactly 3 line segments to form a non-degenerate triangle. Mahmoud doesn’t accept challenges unless he is sure he can win, so he asked you to tell him if he should accept the challenge. Given the lengths of the line segments, check if he can choose exactly 3 of them to form a non-degenerate triangle.
Mahmoud should use exactly 3 line segments, he can’t concatenate two line segments or change any length. A non-degenerate triangle is a triangle with positive area.
Input
The first line contains single integer n (3 ≤ n ≤ 105) — the number of line segments Mahmoud has.
The second line contains n integers a1, a2, …, a**n (1 ≤ a**i ≤ 109) — the lengths of line segments Mahmoud has.
Output
In the only line print “YES” if he can choose exactly three line segments and form a non-degenerate triangle with them, and “NO” otherwise.
Examples
input
5
1 5 3 2 4
output
YES
input
3
4 1 2
output
NO
Note
For the first example, he can use line segments with lengths 2, 4 and 5 to form a non-degenerate triangle.
给你n条边;
问你能不能从中挑出3条边来组成一个三角形
#include<cstring>
#include<algorithm>
#include<cstdio>
#include<vector>
#define pb push_back
using namespace std;
const int N = 301010;
int n,i,a[N];
int main(){
scanf("%d",&n);
for (i=1;i<=n;i++){
scanf("%d",&a[i]);
}
sort(a+1,a+1+n);
for (i=1;i<n-1;i++)
if (a[i]+a[i+1]>a[i+2]){
printf("YES\n");
return 0;
}
printf("NO");
}
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