Problem Description
Explanation
To solve this problem, we can iterate through the binary string and count the continuous sequences of 1s. For every sequence of length n, the number of substrings that can be formed using that sequence is (n * (n + 1)) / 2. We calculate this for each sequence of 1s and sum up the results to get the total number of substrings with only 1s.
Solutions
class Solution {
public int numSub(String s) {
int count = 0;
int result = 0;
int mod = 1000000007;
for (char c : s.toCharArray()) {
if (c == '1') {
count++;
} else {
result = (result + (count * (count + 1) / 2) % mod) % mod;
count = 0;
}
}
result = (result + (count * (count + 1) / 2) % mod) % mod;
return result;
}
}Loading editor...