【codeforces 894A】QAQ
A. QAQ【題目鏈接】
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standard output
"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?n. There is a great number of "QAQ" in the string (Diamond is so cute!).
illustration by 貓屋 https://twitter.com/nekoyaliu
Bort 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.
Input
The only line contains a string of length?n?(1?≤?n?≤?100). It's guaranteed that the string only contains uppercase English letters.
Output
Print a single integer?— the number of subsequences "QAQ" in the string.
Examples
input
Copy
QAQAQYSYIOIWINoutput
Copy
4input
Copy
QAQQQZZYNOIWINoutput
Copy
3Note
In the first example there are?4?subsequences "QAQ": "QAQAQYSYIOIWIN", "QAQAQYSYIOIWIN", "QAQAQYSYIOIWIN", "QAQAQYSYIOIWIN".
將每個'A'兩邊的'Q'個數(shù)相乘之后加和即可
#include<bits/stdc++.h> using namespace std; typedef long long ll;int main() {ll n;string s;ll i;cin>>s;ll q=0;ll l=s.length();for(i=0;i<l;i++){if(s[i]=='Q') q++;}ll ans=0;ll temp=0;for(i=0;i<l;i++){if(s[i]=='Q')temp++;if(s[i]=='A'){ans+=temp*(q-temp);}}cout<<ans<<endl;return 0; }?
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