Create 2707-extra-characters-in-a-string.cpp

Author: Abe0770

cpp/2707-extra-characters-in-a-string.cpp

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+/*
+  You are given a 0-indexed string s and a dictionary of words dictionary. 
+  You have to break s into one or more non-overlapping substrings such that each substring is present in dictionary. 
+  There may be some extra characters in s which are not present in any of the substrings.
+
+  Return the minimum number of extra characters left over if you break up s optimally.
+
+  Ex. Input: s = "leetscode", dictionary = ["leet","code","leetcode"]
+      Output: 1
+      Explanation: We can break s in two substrings: "leet" from index 0 to 3 and "code" from index 5 to 8. There is only 1 unused character (at index 4), so we return 1.
+
+  Time  : O(N^M)    M = dictionary.size(), N = s.size()
+  Space : O(N)
+*/
+
+class Solution {
+public:
+    int minExtraChar(string s, vector<string>& dictionary) {
+        int n = s.size();
+        vector<int> dp(n + 1, n);
+
+        dp[0] = 0; 
+
+        for (int i = 1; i <= n; ++i) {
+            for(int j = 0 ; j < dictionary.size() ; ++j) {
+                int len = dictionary[j].size();
+                if (i >= len && s.substr(i - len, len) == dictionary[j]) {
+                    dp[i] = min(dp[i], dp[i - len]);
+                }
+            }
+            dp[i] = min(dp[i], dp[i - 1] + 1);
+        }
+
+        return dp[n];
+    }
+};