Codeforces Round #409 (rated, Div. 2, based on VK Cup 2017 Round 2)A. Vicious Keyboard
Tonio has a keyboard with only two letters, "V" and "K".
One day, he has typed out a string s with only these two letters. He really likes it when the string "VK" appears, so he wishes to change at most one letter in the string (or do no changes) to maximize the number of occurrences of that string. Compute the maximum number of times "VK" can appear as a substring (i. e. a letter "K" right after a letter "V") in the resulting string.
The first line will contain a string s consisting only of uppercase English letters "V" and "K" with length not less than 1 and not greater than 100.
Output a single integer, the maximum number of times "VK" can appear as a substring of the given string after changing at most one character.
VK
1
VV
1
V
0
VKKKKKKKKKVVVVVVVVVK
3
KVKV
1
For the first case, we do not change any letters. "VK" appears once, which is the maximum number of times it could appear.
For the second case, we can change the second character from a "V" to a "K". This will give us the string "VK". This has one occurrence of the string "VK" as a substring.
For the fourth case, we can change the fourth character from a "K" to a "V". This will give us the string "VKKVKKKKKKVVVVVVVVVK". This has three occurrences of the string "VK" as a substring. We can check no other moves can give us strictly more occurrences.
题目大意:一个字符串只由V和K组成,你可以改变一个字符串最多一个字母,问你最多能得到几个VK
题目解析:单个枚举变的字母,计算VK的个数,记录最大值
#include <bits/stdc++.h> using namespace std; const int MAXN = 100007; int n, m; int main() { string s; cin >> s; n = s.size(); int ans = 0; for(int j = 1; j < n; j++) { if(s[j-1] == 'V' && s[j] == 'K') ans++; } for(int i = 0; i < n; i++) { if(s[i] == 'V') s[i] = 'K'; else if(s[i] == 'K') s[i] = 'V'; int cnt = 0; for(int j = 1; j < n; j++) { if(s[j-1] == 'V' && s[j] == 'K') cnt++; } ans = max(cnt, ans); if(s[i] == 'V') s[i] = 'K'; else if(s[i] == 'K') s[i] = 'V'; } printf("%d\n", ans); return 0; }