CF894A QAQ

題意翻譯

題目大意： 給定一個字符串，字符串長度<=100，現在要求出字符串中'QAQ'的個數，注意，'QAQ'可以不連續，只要有順序就可以了，例如QABQ也有一個QAQ

Translated by @Hjl1777

題目描述

"QAQ" is a word to denote an expression of crying. Imagine "Q" as eyes with tears and "A" as a mouth.

Now Diamond has given Bort a string consisting of only uppercase English letters of length?nn?. There is a great number of "QAQ" in the string (Diamond is so cute!).

illustration by 貓屋?https://twitter.com/nekoyaliuBort?wants to know how many subsequences "QAQ" are in the string Diamond has given. Note that the letters "QAQ" don't have to be consecutive, but the order of letters should be exact.

輸入輸出格式

輸入格式：

?

The only line contains a string of length?nn?(?1<=n<=1001<=n<=100?). It's guaranteed that the string only contains uppercase English letters.

?

輸出格式：

?

Print a single integer — the number of subsequences "QAQ" in the string.

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輸入輸出樣例

輸入樣例#1：?復制 QAQAQYSYIOIWIN 輸出樣例#1：?復制 4 輸入樣例#2：?復制 QAQQQZZYNOIWIN 輸出樣例#2：?復制 3

說明

In the first example there are?44?subsequences "QAQ": "QAQAQYSYIOIWIN", "QAQAQYSYIOIWIN", "QAQAQYSYIOIWIN", "QAQAQYSYIOIWIN".

?

思路：組合數學搞一下就可以了。

#include<cstdio> #include<cstring> #include<iostream> #include<algorithm> using namespace std; string s; int ans,t,q[100]; int main(){cin>>s;int len=s.size();for(int i=0;i<s.size();++i) q[i]=s[i]=='Q'?++t:t;for(int i=0;i<s.size();++i) if(s[i]=='A') ans+=q[i]*(t-q[i]);cout<<ans; }

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轉載于:https://www.cnblogs.com/cangT-Tlan/p/8441357.html

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