Get the smallest number from given digit [closed] - c++

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i'm trying to get the smallest and the biggest number possible by rearanging the 3 digit number.
So i success get the biggest
int maxNumFromNum(int num) {
int freq[10] = {0};
string str = to_string(num);
for (int i = 0; i < str.length(); i++)
freq[str[i] - '0']++;
int res = 0, mul = 1;
for (int i = 0; i <= 9; i++) {
while (freq[i] > 0) {
res = res + (i * mul);
freq[i]--;
mul = mul * 10;
}
}
return res;
}
But now i'm trying to get the smallest one. How can be done that.
Example Outpots:
321 Output> 123, 321
598 Output> 985, 598.
And too, is there more efficiency way to do that?
Thanks in advice.

Answer 1

A simple solution:
#include<bits/stdc++.h>
using namespace std;
int main() {
int n = 231;
string s = to_string(n);
sort(s.begin(), s.end());
cout<<"Smaller: "<<s<<endl;
reverse(s.begin(), s.end());
cout<<"Bigger : "<<s<<endl;
}
It works for integers of any size and runs in O(n lg(n)), where n is the number of digits of the integer.

Answer 2

You could simply change the line:
for (int i = 0; i <= 9; i++) {
to
for (int i = 9; i >= 0; i--) {

Answer 3

void getBigAndSmall(string num, string &outBig, string outSmall){
outBig = 0;
outSmall = 0;
//since you're sorting digits you can use this to sort them with O(n)
//this would be faster than std::sort in this case.
int bigArray[10] = {0};
int smallArray[10] = {0};
for (int i = 0; i < 10; i++){
int digit = (int)num[i] - 48; //this might not be good idea.
bigArray[digit]++;
smallArray[digit]++;
}
int digitsSize = num.size();
for (int i = 0; i < digitsSize; i++){
for (int j = 0; j < 10; j++){
if (bigArray[j] > 0){
bigArray[j]--;
outBig += j;
}
}
for (int j = 9; j > -1; j--){
if (smallArray[j] > 0){
smallArray[j]--;
outSmall += j;
}
}
}
}
This might have some mistakes, since I didn't test it, but it has a runtime O(n).

Answer 4

It gives max integer using input digits without using string
int extractMax(int num) {
std::vector<int> digits;
bool flag = false;
int curDigit;
while (num > 0) {
curDigit = num % 10;
num /= 10;
flag = false;
for (int i = 0; i < digits.size(); ++i) {
if (digits[i] > curDigit) {
flag = true;
digits.insert(digits.begin() + i, curDigit);
break;
}
}
if (not flag) digits.push_back(curDigit);
}
std::sort(digits.begin(), digits.end());
int dec = 1, int_val = 0;
for (auto& it : digits){
int_val += it * dec;
dec *= 10;
}
return int_val;
}
If you want to get smallest integer, change this line:
std::sort(digits.begin(), digits.end());
With this:
std::sort(digits.begin(), digits.end(), greater<int>());