A. Mahmoud and Longest Uncommon Subsequence
time limit per test:2 seconds
memory limit per test:256 megabytes
input:standard input
output:standard output
While Mahmoud and Ehab were PRacticing for IOI, they found a problem which name was Longest common subsequence. They solved it, and then Ehab challenged Mahmoud with another problem.
Given two strings a and b, find the length of their longest uncommon subsequence, which is the longest string that is a subsequence of one of them and not a subsequence of the other.
A subsequence of some string is a sequence of characters that appears in the same order in the string, The appearances don’t have to be consecutive, for example, strings “ac”, “bc”, “abc” and “a” are subsequences of string “abc” while strings “abbc” and “acb” are not. The empty string is a subsequence of any string. Any string is a subsequence of itself.
Input
The first line contains string a, and the second line — string b. Both of these strings are non-empty and consist of lowercase letters of English alphabet. The length of each string is not bigger than 105 characters.
Output
If there’s no uncommon subsequence, print “-1”. Otherwise print the length of the longest uncommon subsequence of a and b.
Examples
Input abcd defgh
Output 5
Input a a
Output -1
Note
In the first example: you can choose “defgh” from string b as it is the longest subsequence of string b that doesn’t appear as a subsequence of string a. 题意:判断两个串的最长不公共子序列。 题解:-1或者最长的串。 代码:
#include<bits/stdc++.h>using namespace std;string a,b;int main(){ cin>>a>>b; if(a!=b) cout<<max(a.length(),b.length()); else cout<<"-1"<<endl;}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 ai. 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, …, an (1 ≤ ai ≤ 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. 题意:任取三个数,问能否构成不退化三角形。 题解:排个序判断一下即可。 代码:
#include <bits/stdc++.h>#define ll long longusing namespace std;const int N=1e5+10;ll a[N];int main(){ int n; cin>>n; for(int i=1; i<=n; i++) cin>>a[i]; sort(a+1,a+1+n); bool flag=false; for(int i=2; i<n; i++) { if(a[i]+a[i-1]>a[i+1]) flag=true; } if(flag) cout<<"YES"<<endl; else cout<<"NO"<<endl;}新闻热点
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