{ "data": { "question": { "questionId": "2225", "questionFrontendId": "2083", "categoryTitle": "Algorithms", "boundTopicId": 1120944, "title": "Substrings That Begin and End With the Same Letter", "titleSlug": "substrings-that-begin-and-end-with-the-same-letter", "content": null, "translatedTitle": "求以相同字母开头和结尾的子串总数", "translatedContent": null, "isPaidOnly": true, "difficulty": "Medium", "likes": 3, "dislikes": 0, "isLiked": null, "similarQuestions": "[]", "contributors": [], "langToValidPlayground": null, "topicTags": [ { "name": "Hash Table", "slug": "hash-table", "translatedName": "哈希表", "__typename": "TopicTagNode" }, { "name": "Math", "slug": "math", "translatedName": "数学", "__typename": "TopicTagNode" }, { "name": "String", "slug": "string", "translatedName": "字符串", "__typename": "TopicTagNode" }, { "name": "Counting", "slug": "counting", "translatedName": "计数", "__typename": "TopicTagNode" }, { "name": "Prefix Sum", "slug": "prefix-sum", "translatedName": "前缀和", "__typename": "TopicTagNode" } ], "companyTagStats": null, "codeSnippets": null, "stats": "{\"totalAccepted\": \"228\", \"totalSubmission\": \"365\", \"totalAcceptedRaw\": 228, \"totalSubmissionRaw\": 365, \"acRate\": \"62.5%\"}", "hints": [ "In the string \"abacad\", the letter \"a\" appears 3 times. How many substrings begin with the first \"a\" and end with any \"a\"?", "There are 3 substrings (\"a\", \"aba\", and \"abaca\"). How many substrings begin with the second \"a\" and end with any \"a\"? How about the third?", "2 substrings begin with the second \"a\" (\"a\", and \"aca\") and 1 substring begins with the third \"a\" (\"a\").", "There is a total of 3 + 2 + 1 = 6 substrings that begin and end with \"a\".", "If a character appears i times in the string, there are i * (i + 1) / 2 substrings that begin and end with that character." ], "solution": null, "status": null, "sampleTestCase": "\"abcba\"", "metaData": "{\n \"name\": \"numberOfSubstrings\",\n \"params\": [\n {\n \"name\": \"s\",\n \"type\": \"string\"\n }\n ],\n \"return\": {\n \"type\": \"long\"\n }\n}", "judgerAvailable": true, "judgeType": "large", "mysqlSchemas": [], "enableRunCode": true, "envInfo": "{\"cpp\":[\"C++\",\"

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