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intToRoman.cc
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intToRoman.cc
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#include<iostream>
#include<string>
using namespace std;
class Solution {
public:
/*string intToRoman(int num) {
string ret("");
if (!num)
return ret;
int base = 10;
while ((num % base) == 0) base *= 10;
// for the number only the first digit is not 0
if (base > num) {
string one;
string ten;
string five;
if (base == 10) {
one = 'I';
five = 'V';
ten = 'X';
} else if (base == 100) {
one = 'X';
five = 'L';
ten = 'C';
} else if (base == 1000) {
one = 'C';
five = 'D';
ten = 'M';
} else {
one = 'M'; // because input < 3999
}
int first = (num / (base / 10) )% 10;
switch(first) {
case 1:
return one;
case 2:
return one + one;
case 3:
return one + one + one;
case 4:
return one + five;
case 5:
return five;
case 6:
return five + one;
case 7:
return five + one + one;
case 8:
return five + one + one + one;
case 9:
return one + ten;
}
} else {
int cur = num % base;
int pre = num - cur;
return intToRoman(pre) + intToRoman(cur);
}*/
//iterative way.
string intToRoman(int num) {
if (!num) return "";
int base = 1000;
string ret = "";
while (base > 0) {
int cur = num / base;
num -= cur * base;
string one, five, ten;
switch (base) {
case 1:
one = "I";
five = "V";
ten = "X";
break;
case 10:
one = "X";
five = "L";
ten = "C";
break;
case 100:
one = "C";
five = "D";
ten = "M";
break;
case 1000:
one = "M";
break;
}
if (cur <= 3) {
for (int i = 0; i < cur; i++) ret += one;
} else if (cur == 4) {
ret += one + five;
} else if (cur < 9) {
ret += five;
for (int i = 0; i < cur - 5; i++) ret += one;
} else {
ret += one + ten;
}
base /= 10;
}
return ret;
}
};