From 3048b00d72146838275c37ec549b76eeca8813a9 Mon Sep 17 00:00:00 2001
From: speed <speed@mail.ustc.edu.cn>
Date: Thu, 7 Apr 2022 10:52:27 +0800
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---
 problems/0763.划分字母区间.md | 28 ++++++++++++++++++----------
 1 file changed, 18 insertions(+), 10 deletions(-)

diff --git a/problems/0763.划分字母区间.md b/problems/0763.划分字母区间.md
index d3958bd5..d350f255 100644
--- a/problems/0763.划分字母区间.md
+++ b/problems/0763.划分字母区间.md
@@ -90,35 +90,43 @@ public:
         return a[0] < b[0];
     }
     // 记录每个字母出现的区间
-    void countLabels(string s, vector<vector<int>> &hash) {
+    vector<vector<int>> countLabels(string s) {
+        vector<vector<int>> hash(26, vector<int>(2, INT_MIN));
+        vector<vector<int>> hash_filter;
         for (int i = 0; i < s.size(); ++i) {
             if (hash[s[i] - 'a'][0] == INT_MIN) {
                 hash[s[i] - 'a'][0] = i;
             }
             hash[s[i] - 'a'][1] = i;
         }
+        // 去除字符串中未出现的字母所占用区间
+        for (int i = 0; i < hash.size(); ++i) {
+            if (hash[i][0] != INT_MIN) {
+                hash_filter.push_back(hash[i]);
+            }
+        }
+        return hash_filter;
     }
     vector<int> partitionLabels(string s) {
         vector<int> res;
-        vector<vector<int>> hash(26, vector<int>(2, INT_MIN));
-        countLabels(s, hash);
+        // 这一步得到的 hash 即为无重叠区间题意中的输入样例格式：区间列表
+        // 只不过现在我们要求的是区间分割点
+        vector<vector<int>> hash = countLabels(s);
         // 按照左边界从小到大排序
         sort(hash.begin(), hash.end(), cmp);
         // 记录最大右边界
-        int rightBoard = INT_MIN;
+        int rightBoard = hash[0][1];
         int leftBoard = 0;
-        for (int i = 0; i < hash.size(); ++i) {
-            // 过滤掉字符串中没有的字母
-            if (hash[i][0] == INT_MIN) {
-                continue;
-            }
+        for (int i = 1; i < hash.size(); ++i) {
+            // 由于字符串一定能分割，因此,
             // 一旦下一区间左边界大于当前右边界，即可认为出现分割点
-            if (rightBoard != INT_MIN && hash[i][0] > rightBoard) {
+            if (hash[i][0] > rightBoard) {
                 res.push_back(rightBoard - leftBoard + 1);
                 leftBoard = hash[i][0];
             }
             rightBoard = max(rightBoard, hash[i][1]);
         }
+        // 最右端
         res.push_back(rightBoard - leftBoard + 1);
         return res;
     }