CC150 1.3 ReplaceSpaces

Write a method to replace all spaces in a string with '%20', You may assume that the string has sufficient space at the end to hod the additional characters, and you are given "true" length of the string.

要求： In place， 即不能另外开辟空间；

思路： 从后向前； 优点： in place

步骤： 1 循环，找出空格的个数；据此推算新数组元素的个数  2 实际操作翻转，编辑字符串，看到空格，就替换为%20 

C# 代码：

public static void ReplaceSpaces(char[] str, int length) { int spaceCount = 0, newLength; for ( int i = 0; i < length; i++) { if (str[i] == ' ') spaceCount++; } newLength = length + spaceCount * 2; for ( int i = length - 1; i >= 0; i--) { if (str[i] == ' ') { str[newLength - 1] = '0'; str[newLength - 2] = '2'; str[newLength - 3] = '%'; newLength = newLength - 3; } else { //复制内容 str[newLength - 1] = str[i]; //指针左移1位 newLength = newLength - 1; } } }