剑指offer面试题：替换空格

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题目：请实现一个函数，把字符串中的每个空格替换成“%20”。例如输入“We are happy.”，则输出“We%20are%20happy.”。

解析：时间复杂度为O(n)的解法。

完整代码及测试用例实现：

#include<iostream>using namespace std;#include <cstring>//length 为字符数组string的总容量void ReplaceBlank(char string[], int length){if (string == NULL&&length <= 0){return;}//reallyLength 为字符串string的实际长度int reallyLength = 0, numberOfBlank = 0,i=0;while (string[i]!='\0'){++reallyLength;if (string[i] == ' '){++numberOfBlank;}++i;}//newLength 为把空格替换成'%20'之后的长度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;}}// ====================测试代码====================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(){// 空格在句子中间const int length = 100;char string[length] = "we are happy.";Test("Test1", string, length, "we%20are%20happy.");}void Test2(){// 空格在句子开头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(){// 连续有两个空格const int length = 100;char string[length] = "we  are happy.";Test("Test4", string, length, "we%20%20are%20happy.");}void Test5(){// 传入NULLTest("Test5", NULL, 0, NULL);}void Test6(){// 传入内容为空的字符串const int length = 100;char string[length] = "";Test("Test6", string, length, "");}void Test7(){//传入内容为一个空格的字符串const int length = 100;char string[length] = " ";Test("Test7", string, length, "%20");}void Test8(){// 传入的字符串没有空格const int length = 100;char string[length] = "wearehappy.";Test("Test8", string, length, "wearehappy.");}void Test9(){// 传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;}

运行结果：

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.

请按任意键继续. . .

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