add 3144

Author: yinghaoyu

README.md

@@ -259,6 +259,7 @@ LeetCode Solution In Hard Way
 |3151|[Special Array I](https://leetcode.cn/problems/special-array-i/) | [C++](./src/Problem_3151_isArraySpecial.cc)|Easy|
 |3148|[Maximum Difference Score in a Grid](https://leetcode.cn/problems/maximum-difference-score-in-a-grid/) | [C++](./src/Problem_3148_maxScore.cc)|Medium|
 |3145|[Maximum Difference Score in a Grid](https://leetcode.cn/problems/find-products-of-elements-of-big-array/) | [C++](./src/Problem_3145_findProductsOfElements.cc)|Hard|
+|3144|[Minimum Substring Partition of Equal Character Frequency](https://leetcode.cn/problems/minimum-substring-partition-of-equal-character-frequency/) | [C++](./src/Problem_3144_minimumSubstringsInPartition.cc)|Medium|
 |3134|[Find the Median of the Uniqueness Array](https://leetcode.cn/problems/find-the-median-of-the-uniqueness-array/) | [C++](./src/Problem_3134_medianOfUniquenessArray.cc)|Hard|
 |3131|[Find the Integer Added to Array I](https://leetcode.cn/problems/find-the-integer-added-to-array-i/) | [C++](./src/Problem_3131_addedInteger.cc)|Easy|
 |3117|[Minimum Sum of Values by Dividing Array](https://leetcode.cn/problems/minimum-sum-of-values-by-dividing-array/) | [C++](./src/Problem_3117_minimumValueSum.cc)|Hard|

src/Problem_3144_minimumSubstringsInPartition.cc

@@ -0,0 +1,75 @@
+#include <cstdint>
+#include <string>
+#include <vector>
+
+using namespace std;
+
+class Solution
+{
+ public:
+  // 记忆化搜索
+  int minimumSubstringsInPartition1(string s)
+  {
+    int n = s.length();
+    // dp[i] 的含义为 s[0...i]内，最少能分割多少个平衡子串
+    vector<int> dp(n, -1);
+    return dfs(n - 1, s, dp);
+  }
+
+  int dfs(int i, string& s, vector<int>& dp)
+  {
+    if (i < 0)
+    {
+      return 0;
+    }
+    if (dp[i] != -1)
+    {
+      return dp[i];
+    }
+    int ans = INT32_MAX;
+    vector<int> cnt(26);
+    // 不同字符种类
+    int k = 0;
+    // 字符计数的最大值
+    int max = 0;
+    for (int j = i; j >= 0; j--)
+    {
+      // 新字符加入
+      k += cnt[s[j] - 'a']++ == 0;
+      // 字符计数最大值
+      max = std::max(max, cnt[s[j] - 'a']);
+      // 检查是否每个字符的计数都一样
+      if (i - j + 1 == k * max)
+      {
+        // 如果 s[i...j] 是平衡字符串，那么讨论子问题s[0...j-1]
+        ans = std::min(ans, dfs(j - 1, s, dp) + 1);
+      }
+    }
+    dp[i] = ans;
+    return ans;
+  }
+
+  // 动态规划
+  int minimumSubstringsInPartition2(string s)
+  {
+    int n = s.length();
+    vector<int> dp(n + 1, INT32_MAX);
+    dp[0] = 0;
+    for (int i = 0; i < n; i++)
+    {
+      vector<int> cnt(26);
+      int k = 0;
+      int max = 0;
+      for (int j = i; j >= 0; j--)
+      {
+        k += cnt[s[j] - 'a']++ == 0;
+        max = std::max(max, cnt[s[j] - 'a']);
+        if (i - j + 1 == k * max)
+        {
+          dp[i + 1] = std::min(dp[i + 1], dp[j] + 1);
+        }
+      }
+    }
+    return dp[n];
+  }
+};