LeetCode 696. Count Binary Substrings

考点	难度
String	Easy

题目

Give a binary string s, return the number of non-empty 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.

思路

持续更新prevRunLength和curRunLength，只要prevRunLength >= curRunLength答案就加一。

答案

public int countBinarySubstrings(String s) {
        int prevRunLength = 0, curRunLength = 1, res = 0;
        for (int i=1;i<s.length();i++) {
            if (s.charAt(i) == s.charAt(i-1)) curRunLength++;
            else {
                prevRunLength = curRunLength;
                curRunLength = 1;
            }
            if (prevRunLength >= curRunLength) res++;
        }
        return res;
}