本文基于Free Code Camp基本算法腳本“查找字符串中最長的單詞”。
在此算法中，我們要查看每個單詞并計算每個單詞中有多少個字母。然后，比較計數以確定哪個單詞的字符最多，并返回最長單詞的長度。
在本文中，我將解釋三種方法。首先使用FOR循環，其次使用sort（）方法，第三次使用reduce（）方法。
算法挑戰
- 返回提供的句子中最長單詞的長度。
- 您的回復應該是一個數字。
提供的測試用例
- findLongestWord(“The quick brown fox jumped over the lazy dog”)返回一個數字
- findLongestWord(“The quick brown fox jumped over the lazy dog”)返回6
- findLongestWord(“May the force be with you”)返回5
- findLongestWord(“Google do a barrel roll”)返回6
- findLongestWord(“What is the average airspeed velocity of an unladen swallow”)返回8
- findLongestWord(“What if we try a super-long word such as otorhinolaryngology”)返回19
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function findLongestWord(str) { return str.length;}findLongestWord("The quick brown fox jumped over the lazy dog"); |
1.使用FOR循環查找最長的單詞
對于此解決方案，我們將使用String.prototype.split（）方法
- split()的方法通過分離串分成子串分割字符串對象到字符串數組。
我們將需要在split（）方法的括號之間添加一個空格
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var strSplit = “The quick brown fox jumped over the lazy dog”.split(‘ ‘); |
它將輸出一個由單詞組成的數組：
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var strSplit = [“The”, “quick”, “brown”, “fox”, “jumped”, “over”, “the”, “lazy”, “dog”]; |
如果不在括號中添加空格，則將得到以下輸出：
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var strSplit = [“T”, “h”, “e”, “ “, “q”, “u”, “i”, “c”, “k”, “ “, “b”, “r”, “o”, “w”, “n”, “ “, “f”, “o”, “x”, “ “, “j”, “u”, “m”, “p”, “e”, “d”, “ “, “o”, “v”, “e”, “r”, “ “, “t”, “h”, “e”, “ “, “l”, “a”, “z”, “y”, “ “, “d”, “o”, “g”]; |
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function findLongestWord(str) { // Step 1. Split the string into an array of strings var strSplit = str.split(' '); // var strSplit = "The quick brown fox jumped over the lazy dog".split(' '); // var strSplit = ["The", "quick", "brown", "fox", "jumped", "over", "the", "lazy", "dog"]; // Step 2. Initiate a variable that will hold the length of the longest word var longestWord = 0; // Step 3. Create the FOR loop for(var i = 0; i < strSplit.length; i++){ if(strSplit[i].length > longestWord){ // If strSplit[i].length is greater than the word it is compared with... longestWord = strSplit[i].length; // ...then longestWord takes this new value } } /* Here strSplit.length = 9 For each iteration: i = ? i < strSplit.length? i++ if(strSplit[i].length > longestWord)? longestWord = strSplit[i].length 1st iteration: 0 yes 1 if("The".length > 0)? => if(3 > 0)? longestWord = 3 2nd iteration: 1 yes 2 if("quick".length > 3)? => if(5 > 3)? longestWord = 5 3rd iteration: 2 yes 3 if("brown".length > 5)? => if(5 > 5)? longestWord = 5 4th iteration: 3 yes 4 if("fox".length > 5)? => if(3 > 5)? longestWord = 5 5th iteration: 4 yes 5 if("jumped".length > 5)? => if(6 > 5)? longestWord = 6 6th iteration: 5 yes 6 if("over".length > 6)? => if(4 > 6)? longestWord = 6 7th iteration: 6 yes 7 if("the".length > 6)? => if(3 > 6)? longestWord = 6 8th iteration: 7 yes 8 if("lazy".length > 6)? => if(4 > 6)? longestWord = 6 9th iteration: 8 yes 9 if("dog".length > 6)? => if(3 > 6)? longestWord = 6 10th iteration: 9 no End of the FOR Loop*/ //Step 4. Return the longest word return longestWord; // 6}findLongestWord("The quick brown fox jumped over the lazy dog"); |
沒有注釋：
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function findLongestWord(str) { var strSplit = str.split(' '); var longestWord = 0; for(var i = 0; i < strSplit.length; i++){ if(strSplit[i].length > longestWord){ longestWord = strSplit[i].length; } } return longestWord;}findLongestWord("The quick brown fox jumped over the lazy dog"); |
2.使用sort（）方法找到最長的單詞
對于此解決方案，我們將使用Array.prototype.sort（）方法按照某種排序標準對數組進行排序，然后返回此數組的第一個元素的長度。
- sort()的方法進行排序的陣列的代替元素并返回數組。
就我們而言，如果我們只是對數組排序
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var sortArray = [“The”, “quick”, “brown”, “fox”, “jumped”, “over”, “the”, “lazy”, “dog”].sort(); |
我們將得到以下輸出：
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var sortArray = [“The”, “brown”, “dog”, “fox”, “jumped”, “lazy”, “over”, “quick”, “the”]; |
在Unicode中，數字在大寫字母之前，而在小寫字母之前。
我們需要按照某種排序標準對元素進行排序
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[].sort(function(firstElement, secondElement) { return secondElement.length — firstElement.length; }) |
比較第二個元素的長度和數組中第一個元素的長度。
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function findLongestWord(str) { // Step 1. Split the string into an array of strings var strSplit = str.split(' '); // var strSplit = "The quick brown fox jumped over the lazy dog".split(' '); // var strSplit = ["The", "quick", "brown", "fox", "jumped", "over", "the", "lazy", "dog"]; // Step 2. Sort the elements in the array var longestWord = strSplit.sort(function(a, b) { return b.length - a.length; }); /* Sorting process a b b.length a.length var longestWord "The" "quick" 5 3 ["quick", "The"] "quick" "brown" 5 5 ["quick", "brown", "The"] "brown" "fox" 3 5 ["quick", "brown", "The", "fox"] "fox" "jumped" 6 3 ["jumped", quick", "brown", "The", "fox"] "jumped" "over" 4 6 ["jumped", quick", "brown", "over", "The", "fox"] "over" "the" 3 4 ["jumped", quick", "brown", "over", "The", "fox", "the"] "the" "lazy" 4 3 ["jumped", quick", "brown", "over", "lazy", "The", "fox", "the"] "lazy" "dog" 3 4 ["jumped", quick", "brown", "over", "lazy", "The", "fox", "the", "dog"] */ // Step 3. Return the length of the first element of the array return longestWord[0].length; // var longestWord = ["jumped", "quick", "brown", "over", "lazy", "The", "fox", "the", "dog"]; // longestWord[0]="jumped" => jumped".length => 6}findLongestWord("The quick brown fox jumped over the lazy dog"); |
沒有注釋：
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function findLongestWord(str) { var longestWord = str.split(' ').sort(function(a, b) { return b.length - a.length; }); return longestWord[0].length;}findLongestWord("The quick brown fox jumped over the lazy dog"); |
3.使用reduce（）方法找到最長的單詞
對于此解決方案，我們將使用Array.prototype.reduce（）。
- reduce()的方法應用于對一個儲液器的功能和所述陣列的每一值（從左到右），以將其降低到一個值。
reduce（）對數組中存在的每個元素執行一次回調函數。
您可以提供一個初始值作為要減少的第二個參數，這里我們將添加一個空字符串“”。
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[].reduce(function(previousValue, currentValue) {...}, “”); |
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function findLongestWord(str) { // Step 1. Split the string into an array of strings var strSplit = str.split(' '); // var strSplit = "The quick brown fox jumped over the lazy dog".split(' '); // var strSplit = ["The", "quick", "brown", "fox", "jumped", "over", "the", "lazy", "dog"]; // Step 2. Use the reduce method var longestWord = strSplit.reduce(function(longest, currentWord) { if(currentWord.length > longest.length) return currentWord; else return longest; }, ""); /* Reduce process currentWord longest currentWord.length longest.length if(currentWord.length > longest.length)? var longestWord "The" "" 3 0 yes "The" "quick" "The" 5 3 yes "quick" "brown" "quick" 5 5 no "quick" "fox" "quick" 3 5 no "quick" "jumped" "quick" 6 5 yes "jumped" "over" "jumped" 4 6 no "jumped" "the" "jumped" 3 6 no "jumped" "lazy" "jumped" 4 6 no "jumped" "dog" "jumped" 3 6 no "jumped" */ // Step 3. Return the length of the longestWord return longestWord.length; // var longestWord = "jumped" // longestWord.length => "jumped".length => 6}findLongestWord("The quick brown fox jumped over the lazy dog"); |
沒有注釋：
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function findLongestWord(str) { var longestWord = str.split(' ').reduce(function(longest, currentWord) { return currentWord.length > longest.length ? currentWord : longest; }, ""); return longestWord.length;}findLongestWord("The quick brown fox jumped over the lazy dog"); |
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原文鏈接：https://blog.csdn.net/qq_25879801/article/details/111408976
