https://blog.csdn.net/yanxiaolx/article/details/52235212

?題目：請實現一個函數，把字符串中的每個空格替換成“%20”。例如輸入“We are happy.”，則輸出“We%20are%20happy.”。

解析：時間復雜度為O(n)的解法。

完整代碼及測試用例實現：

[cpp]?view plaincopy

#include<iostream>??

using?namespace?std;??

#include?<cstring>??

??

//length?為字符數組string的總容量??

void?ReplaceBlank(char?string[],?int?length)??

{??

????if?(string?==?NULL&&length?<=?0)??

????{??

????????return;??

????}??

????//reallyLength?為字符串string的實際長度??

????int?reallyLength?=?0,?numberOfBlank?=?0,i=0;??

??????

????while?(string[i]!='\0')??

????{??

????????++reallyLength;??

??

????????if?(string[i]?==?'?')??

????????{??

????????????++numberOfBlank;??

????????}??

????????++i;??

????}??

??

????//newLength?為把空格替換成'%20'之后的長度??

????int?newLength?=?reallyLength?+?numberOfBlank?*?2;??

????if?(newLength?>?length)??

????{??

????????return;??

????}??

??

????int?indexOfReally?=?reallyLength;??

????int?indexOfNew?=?newLength;??

????while?(indexOfReally?>=?0?&&?indexOfNew?>indexOfReally)??

????{??

????????if?(string[indexOfReally]?==?'?')??

????????{??

????????????string[indexOfNew--]?=?'0';??

????????????string[indexOfNew--]?=?'2';??

????????????string[indexOfNew--]?=?'%';??

????????}??

????????else??

????????{??

????????????string[indexOfNew--]?=?string[indexOfReally];??

????????}??

??

????????--indexOfReally;??

????}??

}??

??

??

//?====================測試代碼====================??

void?Test(char*?testName,?char?string[],?int?length,?char?expected[])??

{??

????if?(testName?!=?NULL)??

????{??

????????cout?<<?testName?<<?"?begins:?";??

????}??

??

????ReplaceBlank(string,?length);??

??

????if?(expected?==?NULL?&&?string?==?NULL)??

????{??

????????cout?<<?"passed."?<<?endl;??

????}??

????else?if?(expected?==?NULL?&&?string?!=?NULL)??

????{??

????????cout?<<?"failed."?<<?endl;??

????}??

????else?if?(strcmp(string,?expected)?==?0)??

????{??

????????cout?<<?"passed."?<<?endl;??

????}??

????else??

????{??

????????cout?<<?"failed."?<<?endl;??

????}??

}??

??

??

void?Test1()??

{??

????//?空格在句子中間??

????const?int?length?=?100;??

??

????char?string[length]?=?"we?are?happy.";??

????Test("Test1",?string,?length,?"we%20are%20happy.");??

}??

??

??

void?Test2()??

{??

????//?空格在句子開頭??

????const?int?length?=?100;??

??

????char?string[length]?=?"?wearehappy.";??

????Test("Test2",?string,?length,?"%20wearehappy.");??

}??

??

void?Test3()??

{??

????//?空格在句子末尾??

????const?int?length?=?100;??

??

????char?string[length]?=?"wearehappy.?";??

????Test("Test3",?string,?length,?"wearehappy.%20");??

}??

??

void?Test4()??

{??

????//?連續有兩個空格??

????const?int?length?=?100;??

??

????char?string[length]?=?"we??are?happy.";??

????Test("Test4",?string,?length,?"we%20%20are%20happy.");??

}??

??

void?Test5()??

{??

????//?傳入NULL??

????Test("Test5",?NULL,?0,?NULL);??

}??

??

void?Test6()??

{??

????//?傳入內容為空的字符串??

????const?int?length?=?100;??

??

????char?string[length]?=?"";??

????Test("Test6",?string,?length,?"");??

}??

??

void?Test7()??

{??

????//傳入內容為一個空格的字符串??

????const?int?length?=?100;??

??

????char?string[length]?=?"?";??

????Test("Test7",?string,?length,?"%20");??

}??

??

void?Test8()??

{??

????//?傳入的字符串沒有空格??

????const?int?length?=?100;??

??

????char?string[length]?=?"wearehappy.";??

????Test("Test8",?string,?length,?"wearehappy.");??

}??

??

void?Test9()??

{??

????//?傳入的字符串全是空格??

????const?int?length?=?100;??

??

????char?string[length]?=?"???";??

????Test("Test9",?string,?length,?"%20%20%20");??

}??

??

int?main()??

{??

????Test1();??

????Test2();??

????Test3();??

????Test4();??

????Test5();??

????Test6();??

????Test7();??

????Test8();??

????Test9();??

??

????system("pause");???

????return?0;??

}??

運行結果：

Test1 begins: passed.

Test2 begins: passed.

Test3 begins: passed.

Test4 begins: passed.

Test5 begins: passed.

Test6 begins: passed.

Test7 begins: passed.

Test8 begins: passed.

Test9 begins: passed.

請按任意鍵繼續. . .

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