[LeetCode]709. To Lower Case

发表于 | 更新于 | 分类于 | 评论数： | 阅读次数：
字数统计：345 字 | 阅读时长：2 分钟

709. To Lower Case

Implement function ToLowerCase() that has a string parameter str, and returns the same string in lowercase.

题目很简单，说的就是英文字符串，转换成小写。

Example 1:

1
2
Input: "Hello"
Output: "hello"

Example 2:

1
2
Input: "here"
Output: "here"

Example 3:

1
2
Input: "LOVELY"
Output: "lovely"

方案一

首先想到的就是遍历字符串，判断每一个字符是否是大写，如果是大写，则按照ASCII码，转换成小写后，添加到一个新的字符串里；

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
class Solution {
public:
    string toLowerCase(string str) {
        string out;
        for(char &i : str) {
            if ((i >= 65) && (i <= 90)) {
                i=i+32;
                out.push_back(i);
            } else {
                out.push_back(i);
            }
        }
        return out;
    }
};

result

Runtime: 4 ms, faster than 100.00% of C++ online submissions for To Lower Case.

Memory Usage: 8.3 MB, less than 50.42% of C++ online submissions for To Lower Case.

结果看起来还可以，内存占用有点高，想着怎么优化一下；

方案二

string out，占用了一个新建的字符串，是不是可以在原来的字符串里面修改？try try see.

1
2
3
4
5
6
7
8
9
10
11
12
13
class Solution {
public:
    string toLowerCase(string str) {
        unsigned int len = str.length();
        for(unsigned i = 0; i < len; ++i) {
            char ch = str[i];
            if ((ch >= 65) && (ch <= 90)) {
                str[i]=ch+32;
            }
        }
        return str;
    }
};

result

Runtime: 4 ms, faster than 100.00% of C++ online submissions for To Lower Case.

Memory Usage: 8 MB, less than 99.17% of C++ online submissions for To Lower Case.

内存占用降低了点，效果还可以。