1217C. The Number of Good Substrings (thinking)

You will get a binary string s (recall that if each character is 0 or 1, then a string is binary).

 

Let f (t) be the decimal representation of the integer t, written in binary form (may contain leading zeros). For example, f (011) = 3, f (00101) = 5, f (00001) = 1, (10) = 2, f (000) = 0 and f (000100) = 4.

 

If r-l + 1 = f (sl ... sr), the substrings sl, sl + 1, ..., sr are good.

 

For example, the string s = 1011 has 5 substrings: s1 ... s1 = 1, s3 ... s3 = 1, s4 ... s4 = 1, s1 ... s2 = 10, s2 ... s4 = 011.

 

Your task is to count the number of good substrings in the string s.

 

answer:

Find the number of substrings of equal value and length.

The method is to count the number of leading 0s in real time, and then use each number as a starting point to generate a binary string in real time. If you encounter a small length ratio and the number of leading 0s is greater than the difference between the two, it is legal.

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int maxn=2e5+100;
string s;
int main () {
    int T;
    scanf("%d",&T);
    while (T--) {
        cin>>s;
        int ans=0;
        int pre=0;
        for (int i=0;i<s.length();i++) {
            if (s[i]=='0')
                pre++;
            else {
                int r=i;
                int cnt=1;
                for (int j=0;j<18;j++) {
                    if (cnt<=pre+(r-i+1))
                        ans++;
                    if (r==s.length()-1) 
                        break;
                    cnt = cnt * 2 + (s [++ r]- ' 0 ' ); 
                } 
                // Forward extension, if the length is not enough, use the leading 0 
                pre = 0 ; 
            } 
        } 
        printf ( " % d \ n " , ans) ; 
    } 
}