README.md

830. Positions of Large Groups

In a string S of lowercase letters, these letters form consecutive groups of the same character.

For example, a string like S = "abbxxxxzyy" has the groups "a", "bb", "xxxx", "z" and "yy".

Call a group large if it has 3 or more characters. We would like the starting and ending positions of every large group.

The final answer should be in lexicographic order.

Example 1:

Input: "abbxxxxzzy"
Output: [[3,6]]
Explanation: "xxxx" is the single large group with starting  3 and ending positions 6.

Example 2:

Input: "abc"
Output: []
Explanation: We have "a","b" and "c" but no large group.

Example 3:

Input: "abcdddeeeeaabbbcd"
Output: [[3,5],[6,9],[12,14]]

Note: 1 <= S.length <= 1000

Solutions (Rust)

1. Solution

impl Solution {
    pub fn large_group_positions(s: String) -> Vec<Vec<i32>> {
        let mut groups = Vec::new();
        let mut start = 0;
        let mut count = 0;
        let mut cur_ch = ' ';
        for ch in s.chars() {
            if ch == cur_ch {
                count += 1;
            } else if ch != cur_ch {
                if count >= 3 {
                    groups.push(vec![start, start + count - 1]);
                }
                start += count;
                count = 1;
                cur_ch = ch;
            }
        }
        if count >= 3 {
            groups.push(vec![start, start + count - 1]);
        }
        groups
    }
}