【剑指offer】空格替换

Question

设计一种方法，将一个字符串中的所有空格替换成 %20 。你可以假设该字符串有足够的空间来加入新的字符，且你得到的是“真实的”字符长度。

Solution 1

需要额外的一个数组：

class Solution {
public:
    /**
     * @param string: An array of Char
     * @param length: The true length of the string
     * @return: The true length of new string
     */
    int replaceBlank(char string[], int length) {
        // Write your code here
        if(string == NULL || length < 0)
            return -1;
        int ans = length;
        char tmp[1000];
        memcpy(tmp, string, ans);
        for(int i = 0; i < ans; i ++)
        {
            if(string[i] == ‘ ‘)
            {
                for(int j = i + 1; j < ans; j ++)
                {
                    string[j + 2] = tmp[j];
                }

                 string[i] = ‘%‘;
                 string[i + 1] = ‘2‘;
                 string[i + 2 ] = ‘0‘;
                 ans += 2;
                 i += 2;
                 memcpy(tmp, string, ans);
            }

        }

        return ans;
    }
};  

Solution 2

不需要额外的空间，直接在原数组里操作：

class Solution {
public:
    /**
     * @param string: An array of Char
     * @param length: The true length of the string
     * @return: The true length of new string
     */
    int replaceBlank(char string[], int length) {
        // Write your code here
        if(string == NULL || length < 0)
            return -1;

        int blank_num = 0;
        for(int i = 0; i < length; i ++)
        {
            if(string[i] == ‘ ‘)
                blank_num += 1;
        }

        int new_length = length + blank_num * 2;

        int index_new = new_length;
        int index_ori = length;
        while(index_ori >= 0 && index_new > index_ori )
        {
            if(string[index_ori] == ‘ ‘)
            {
                string[index_new--] = ‘0‘;
                string[index_new--] = ‘2‘;
                string[index_new--] = ‘%‘;
            }

            else
                string[index_new--] = string[index_ori];

            index_ori -= 1;
        }

        return new_length;

    }
};