Count Binary Substrings
Description
Give a string s
, count the number of non-empty (contiguous) substrings that have the same number of 0's and 1's, and all the 0's and all the 1's in these substrings are grouped consecutively.
Substrings that occur multiple times are counted the number of times they occur.
Example 1:
Input: "00110011" Output: 6 Explanation: There are 6 substrings that have equal number of consecutive 1's and 0's: "0011", "01", "1100", "10", "0011", and "01".
Notice that some of these substrings repeat and are counted the number of times they occur.
Also, "00110011" is not a valid substring because all the 0's (and 1's) are not grouped together.
Example 2:
Input: "10101" Output: 4 Explanation: There are 4 substrings: "10", "01", "10", "01" that have equal number of consecutive 1's and 0's.
Note:
s.length
will be between 1 and 50,000.s
will only consist of "0" or "1" characters.Solution(javascript)
/** 这题貌似可以用 Prefix Sum 来解, 不行,这题得是连在一起的才行
* @param {string} s
* @return {number}
*/
const countBinarySubstrings = function (s) {
let count = 0
let zeros = 0
let ones = 0
for (let i = 0; i < s.length; i++) {
if (s[i] === '0') {
if (s[i - 1] === '1') {
zeros = 0
}
zeros += 1
if (zeros <= ones) {
count += 1
}
} else {
if (s[i - 1] === '0') {
ones = 0
}
ones += 1
if (ones <= zeros) {
count += 1
}
}
}
return count
}