108 lines
3.2 KiB
C++
108 lines
3.2 KiB
C++
// Source : https://leetcode.com/problems/remove-k-digits/
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// Author : Hao Chen
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// Date : 2016-11-11
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/***************************************************************************************
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*
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* Given a non-negative integer num represented as a string, remove k digits from the
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* number so that the new number is the smallest possible.
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*
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* Note:
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*
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* The length of num is less than 10002 and will be ≥ k.
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* The given num does not contain any leading zero.
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*
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* Example 1:
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*
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* Input: num = "1432219", k = 3
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* Output: "1219"
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* Explanation: Remove the three digits 4, 3, and 2 to form the new number 1219 which
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* is the smallest.
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*
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* Example 2:
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*
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* Input: num = "10200", k = 1
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* Output: "200"
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* Explanation: Remove the leading 1 and the number is 200. Note that the output must
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* not contain leading zeroes.
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*
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* Example 3:
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*
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* Input: num = "10", k = 2
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* Output: "0"
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* Explanation: Remove all the digits from the number and it is left with nothing which
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* is 0.
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***************************************************************************************/
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class Solution {
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public:
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string removeKdigits_pick(string& num, int k) {
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int len = num.size();
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string result;
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int idx = 0;
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for (int i=0; i < len - k; i++) {
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int min_idx = idx;
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for (int j=min_idx; j<=i+k; j++) {
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if (num[min_idx] > num[j]) min_idx = j;
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}
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//don't put zero at the beginning
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if ( !(result.empty() && num[min_idx]=='0') ){
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result.push_back(num[min_idx]);
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}
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//select the number started from next one, to make the order correctness.
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idx = min_idx + 1;
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}
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if (result.empty()) result = "0";
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return result;
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}
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string removeKdigits_remove(string& num, int k) {
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if ( num.size() <= k ) return "0";
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int left_len = num.size() - k;
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int idx = 0;
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for (int i=0; i<k ;i++){
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int len = num.size();
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for (int j=0; j<num.size()-1; j++) {
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//if the current is bigger than next one, then revmoe the current one.
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//In other word, we always pick the smaller one number.
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if ( num[j] > num[j+1] ) {
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num.erase(j, 1);
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idx = j;
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break;
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}
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}
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}
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//remove all of ZEROs at the beginning.
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for (int i=0; i<= num.size(); i++) {
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if (num[i] != '0' || i == num.size()) {
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num.erase(0, i);
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break;
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}
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}
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// if the digits in the array are sorted,
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// then, we need remove the digits at the ends.
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if (num.size() > left_len ) {
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num.erase(num.begin() + left_len, num.end());
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}
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if (num.empty()) num = "0";
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return num;
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}
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string removeKdigits(string num, int k) {
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srand(time(0));
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if (rand() % 2 ) {
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return removeKdigits_pick(num, k);
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} else {
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return removeKdigits_remove(num, k);
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}
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}
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};
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