(Thinking and suffixes and 3 features) K number (2019 cattle off summer school and more training camp (fourth))

Example 1:

Input: 600

Output: 4

说明：'600', '0', '0', '00' are multiples of 300. (Note that '0' are counted twice because it appeared two times)

Example 2:

Input: 123000321013200987000789

Output: 55

Question is intended: to a full string of numeric characters, the number of sub-strings is determined multiple of 300. 0,00,000 and so calculate and consider the preamble is zero.

Solution: Let seeking is a multiple of 300, but then we can split into both a multiple of 3 is a multiple of 100
then so that you can find some rules:
1. For a multiple of three, it is the combined value of the individual bits on and on the answer is 0 3 modulo
two at least 0 2. for each multiple of 100, it is to ask (source: https: //blog.csdn.net/c___c18/article/details/97561689)

So we need to loop on each digital digits were added together, and if it is 0 is 0 and the current one is 0 for special treatment.

AC Code:

 1 #include<bits/stdc++.h>
 2 using namespace std;
 3 const int inf=0x3f3f3f3f,maxn=1e5+5;
 4 char str[maxn];
 5 long long summ,now,a[3],len;
 6 int main()
 7 {
 8     scanf("%s",str);
 9     len=strlen(str);
10     for(int i=len-1;i>=0;i--){
11         now+=str[i]-'0';
12         now%=3;
13         if(str[i]=='0')summ++;
14         if(str[i]=='0'&&str[i+1]=='0'&&i!=len-1){
15             a[now]++;
16         }
17         summ+=a[now];
18     }
19     printf("%lld\n",summ);
20     return 0;
21 }