token.

Solution

Method 1 – String Parsing and Validation

Intuition

We need to check each token in the sentence for the three validity rules. This can be done by iterating through each character and checking for digits, hyphen placement, and punctuation placement.

Approach

Split the sentence into tokens by spaces.
For each token, check:
- No digits present.
- At most one hyphen, and if present, it is surrounded by lowercase letters.
- At most one punctuation mark, and if present, it is at the end.
Count the number of valid tokens.
Return the count.

Code

[{"language":"C++","code":"class Solution {\npublic:\n    int countValidWords(string sentence) {\n        istringstream iss(sentence);\n        string token;\n        int ans = 0;\n        while (iss >> token) {\n            bool valid = true;\n            int hyphen = 0, punct = 0, n = token.size();\n            for (int i = 0; i < n; ++i) {\n                char c = token[i];\n                if (isdigit(c)) { valid = false; break; }\n                if (c == '-') {\n                    hyphen++;\n                    if (hyphen > 1 || i == 0 || i == n-1 || !islower(token[i-1]) || !islower(token[i+1])) { valid = false; break; }\n                }\n                if (c == '!' || c == '.' || c == ',') {\n                    if (i != n-1 || ++punct > 1) { valid = false; break; }\n                }\n            }\n            if (valid) ans++;\n        }\n        return ans;\n    }\n};","lang":"cpp","html":"<pre class=\"shiki shiki-themes github-light github-dark\" style=\"background-color:#fff;--shiki-dark-bg:#24292e;color:#24292e;--shiki-dark:#e1e4e8\" tabindex=\"0\"><code><span class=\"line\"><span style=\"color:#D73A49;--shiki-dark:#F97583\">class</span><span style=\"color:#6F42C1;--shiki-dark:#B392F0\"> Solution</span><span style=\"color:#24292E;--shiki-dark:#E1E4E8\"> {</span></span>\n<span class=\"line\"><span style=\"color:#D73A49;--shiki-dark:#F97583\">public:</span></span>\n<span class=\"line\"><span style=\"color:#D73A49;--shiki-dark:#F97583\">    int</span><span style=\"color:#6F42C1;--shiki-dark:#B392F0\"> countValidWords</span><span style=\"color:#24292E;--shiki-dark:#E1E4E8\">(</span><span style=\"color:#6F42C1;--shiki-dark:#B392F0\">string</span><span style=\"color:#E36209;--shiki-dark:#FFAB70\"> sentence</span><span style=\"color:#24292E;--shiki-dark:#E1E4E8\">) {</span></span>\n<span class=\"line\"><span style=\"color:#24292E;--shiki-dark:#E1E4E8\">        istringstream </span><span style=\"color:#6F42C1;--shiki-dark:#B392F0\">iss</span><span style=\"color:#24292E;--shiki-dark:#E1E4E8\">(sentence);</span></span>\n<span class=\"line\"><span style=\"color:#24292E;--shiki-dark:#E1E4E8\">        string token;</span></span>\n<span class=\"line\"><span style=\"color:#D73A49;--shiki-dark:#F97583\">        int</span><span style=\"color:#24292E;--shiki-dark:#E1E4E8\"> ans </span><span style=\"color:#D73A49;--shiki-dark:#F97583\">=</span><span style=\"color:#005CC5;--shiki-dark:#79B8FF\"> 0</span><span style=\"color:#24292E;--shiki-dark:#E1E4E8\">;</span></span>\n<span class=\"line\"><span style=\"color:#D73A49;--shiki-dark:#F97583\">        while</span><span style=\"color:#24292E;--shiki-dark:#E1E4E8\"> (iss </span><span style=\"color:#D73A49;--shiki-dark:#F97583\">>></span><span style=\"color:#24292E;--shiki-dark:#E1E4E8\"> token) {</span></span>\n<span class=\"line\"><span style=\"color:#D73A49;--shiki-dark:#F97583\">            bool</span><span style=\"color:#24292E;--shiki-dark:#E1E4E8\"> valid </span><span style=\"

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