找规律
先表示个位,分两种情况,大于5,小于5,大于5时特殊处理9, 小于5时特殊处理4
在表示十位,分两种情况,大于50,小于50,大于50特殊处理90, 小于50特殊处理40
...
C++
class Solution {
public:
string intToRoman(int num) {
map<int, string> mp;
mp[0] = "";
mp[1] = "I";
mp[4] = "IV";
mp[5] = "V";
mp[9] = "IX";
mp[10] = "X";
mp[40] = "XL";
mp[50] = "L";
mp[90] = "XC";
mp[100] = "C";
mp[400] = "CD";
mp[500] = "D";
mp[900] = "CM";
mp[1000] = "M";
int t = 10;
vector<string> res;
while (num)
{
string temp = "";
int x = num % t;
if (x >= t / 2)
{
if (x != t - t / 10)
{
temp += mp[t / 2];
x -= t / 2;
while (x)
{
temp += mp[t / 10];
x -= t / 10;
}
}
else
{
temp += mp[t - t / 10];
}
}
else
{
if (x != t / 2 - t / 10)
{
while (x)
{
temp += mp[t / 10];
x -= t / 10;
}
}
else
{
temp += mp[t / 2 - t / 10];
}
}
res.push_back(temp);
num = num - num % t;
t *= 10;
}
string ans = "";
for (int i = res.size() - 1; i >= 0; --i)
{
ans += res[i];
}
return ans;
}
};