402. Remove K Digits - medium
문제
Given a non-negative integer num represented as a string, remove k digits from the number so that the new number is the smallest possible.
제한사항
- The length of num is less than 10002 and will be ≥ k.
- The given num does not contain any leading zero.
입출력 예
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Example 1:
Input: num = "1432219", k = 3
Output: "1219"
Explanation: Remove the three digits 4, 3, and 2 to form the new number 1219 which is the smallest.
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Example 2:
Input: num = "10200", k = 1
Output: "200"
Explanation: Remove the leading 1 and the number is 200. Note that the output must not contain leading zeroes.
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Example 3:
Input: num = "10", k = 2
Output: "0"
Explanation: Remove all the digits from the number and it is left with nothing which is 0.
풀이
- Greedy
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class Solution {
public:
string removeKdigits(string num, int k) {
string answer;
int index = 0;
answer.push_back(num[0]);
for(auto i = 1 ; i < num.size() && k >= 0 ; ++i){
while(!answer.empty() && answer.back() - '0' > num[i] - '0' && k > 0){
answer.pop_back();
--k;
}
answer.push_back(num[i]);
}
for( ; answer.size() && k > 0 ; --k)
answer.pop_back();
size_t first_not_zero = answer.find_first_not_of('0');
return (first_not_zero == string::npos) ? "0" : answer.substr(first_not_zero);
}
};