时间轴

2026-03-20

init

题目：

P763 划分字母区间

https://leetcode.cn/problems/partition-labels/description/?envType=study-plan-v2&envId=top-100-liked

BFS 的做法：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
#include <vector>
#include <string>
#include <queue>

using std::vector;
using std::string;
using std::queue;

class Solution {
    public:
        vector<int> partitionLabels(string s)
        {
                // 1 <= s.length <= 500
                // s 仅由小写英文字母组成
                int i, n = s.size();
                int start = 0;
                vector<int> res;
                vector<int> last_showed_pos(26, -1);

                for (i = n - 1; i >= 0; i--) { // 每个字母最后一次出现的位置
                        if (last_showed_pos[s[i] - 'a'] == -1)
                                last_showed_pos[s[i] - 'a'] = i;
                }

                while (start < n) {
                        queue<char> que;
                        vector<bool> visited(26, false);
                        int len = 0;

                        que.push(s[start]);
                        visited[s[start] - 'a'] = true;

                        while (!que.empty()) {
                                char ch = que.front();
                                que.pop();

                                int boundary = last_showed_pos[ch - 'a'];

                                len = std::max(len, boundary - start + 1);

                                for (i = 0; i <= boundary; i++) {
                                        if (!visited[s[i] - 'a']) {
                                                que.push(s[i]);
                                                visited[s[i] - 'a'] = true;
                                        }
                                }
                        }
                        res.push_back(len);
                        start = start + len;
                }
                return res;
        }
};