代码随想录算法训练营|Day07 LeetCode 344.反转字符串 ，541.反转字符串||，卡玛网54.替换数字

344.反转字符串

344. 反转字符串 - 力扣（LeetCode）

class Solution {
public:
    void reverseString(vector<char>& s) {
 int lens = s.size();
        int right, left;
        if (lens % 2 != 0)//奇数个
        {
            right = lens / 2 +1;
            left = lens / 2 - 1;
        }
        else//偶数个
        {
            right = lens / 2;
            left = lens / 2 - 1;
        }
        int i = 0, j = lens - 1;
        while (i<=left&&j<=lens-1)
        {
            char temp = s[i];
            s[i] = s[j];
            s[j] = temp;
            i++;
            j--;
        }
    }
};

541.反转字符串||

541. 反转字符串 II - 力扣（LeetCode）

class Solution {
public:
    string reverseStr(string s, int k) {
        int len = s.size();
        for (int i =0; i < len; i += 2 * k)
        {
            if (i + k <= s.size())
            {
                reverse(s.begin() + i, s.begin() + i + k);
            }
            else
            {
                reverse(s.begin() + i, s.end());
            }
       }
        return s;
    }
};

卡玛网54.替换数字

54. 替换数字（第八期模拟笔试） (kamacoder.com)### 额外的数组空间

#include<iostream>
#include<string>
using namespace std;

int main()
{
	 string result = "";
	string s;
	cin >> s;
	for (int i = 0; i < s.length(); i++)
	{
		if (s[i] >= 'a' && s[i] <= 'z')
		{
			result += s[i];
		}
		else
		{
			result += "number";
		}
	}
	cout << result;
}

双指针（不借用额外的数组空间）

#include<iostream>
#include<string>
using namespace std;

int main()
{

	string s;
	cin >> s;
	int count = 0;
	int OldIndex = s.size() - 1;
	for (int i = 0; i < s.length(); i++)
	{
		if (s[i] >= '0' && s[i] <= '9')
		{
			count++;
		}
	}
	s.resize(s.size() + count*5);
	int NewIndex = s.size() - 1;//已扩容的下标
	while (OldIndex >= 0)
	{
		if (s[OldIndex] >= '0' && s[OldIndex] <= '9')
		{

			s[NewIndex] = 'r';
			NewIndex--;
			s[NewIndex--] = 'e';
			s[NewIndex--] = 'b';
			s[NewIndex--] = 'm';
			s[NewIndex--] = 'u';
			s[NewIndex--] = 'n';
		}
		else
		{
			s[NewIndex] = s[OldIndex];
			NewIndex--;
		}
		OldIndex--;
	}
	cout << s;
}