字符串和int互转

int转字符串

//实现to_string函数
#include<iostream>
#include<string>
using namespace std;
#define max 100
string to_String(int n)
{
    int m = n;
    char s[max];
    char ss[max];
    int i=0,j=0;
    if (n < 0)// 处理负数
    {
        m = 0 - m;
        j = 1;
        ss[0] = '-';
    }
    while (m>0)
    {
        s[i++] = m % 10 + '0';
        m /= 10;
    }
    s[i] = '\0';
    i = i - 1;
    while (i >= 0)
    {
        ss[j++] = s[i--];
    }
    ss[j] = '\0';
    return ss;
}

int main()
{
    cout << "请输入整数:";
    int m;
    cin >> m;
    string s = to_String(m) + "abc";
    cout << s << endl;
    system("pause");
    return 0;
}

字符串转int：atoi

#include<iostream>
using namespace std;


long long Strtointcode(const char* digit, bool minus)
{
	long long num = 0;
	while (*digit != '\0')
	{
		if (*digit >= '0'&&*digit <= '9')
		{
			int flag = minus ? -1 : 1;
			num = num * 10 + flag * (*digit - '0');
			if ((!minus&&num > 0x7FFFFFFF) || (minus&&num < (signed int)0x80000000))
			{
				num = 0;
				break;
			}
			digit++;
		}
		else
		{
			num = 0;
			break;
		}
	}

	return num;
}

int Strtoint(const char* str)
{

	long long num = 0;
	if (str != NULL && *str != '\0')
	{
		bool minus = false;
		if (*str == '+')
			str++;
		else if (*str == '-')
		{
			str++;
			minus = true;
		}
		if (*str != '\0')
			num = Strtointcode(str, minus);

	}
	return (int)num;
}

int main()
{
	char arr[20];
	int ret = 0;
	
	cin >> arr;
	ret = Strtoint(arr);
	
		cout << ret;
	
	system("pause");
	return 0;
}