https://leetcode.com/problems/remove-k-digits/description/
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.
Note:
- The length of num is less than 10002 and will be ≥ k.
- The given num does not contain any leading zero.
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.
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.
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.
题解:想了很久吧这题,之前用vector但是超时,后来发现string类也有push_back,back,pop_back之类的函数= =
class Solution {
public:
string removeKdigits(string num, int k){
int l = num.length();
int n = l - k;
string v;
v.clear();
if (k >= l || l == 0){
return "0";
}
else if (k <= 0){
return num;
}
for (int i = 0; i < l; i++){
while (k > 0 && num[i] < v.back() && v.size() > 0){
v.pop_back();
k--;
}
v.push_back(num[i]);
}
string ans = "";
for (int i = 0; i < n; i++){
ans += v[i];
}
while (ans[0] == '0'){
ans.erase(0, 1);
}
if (ans.length() != 0){
return ans;
}
else {
return "0";
}
}
};