Create Day 13 Remove K Digits.cpp

Author: tusharjaiswal123

Day 13 Remove K Digits.cpp

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+PROBLEM:
+
+
+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.
+
+
+
+SOLUTION:
+
+
+
+class Solution {
+public:
+    string removeKdigits(string num, int k) {
+        
+        int i;
+        string s;
+        
+        if(k==0)
+            return num;
+        
+        if(k>=num.length())
+        {
+            s="0";
+            return s;
+        }
+        
+        for (const auto c : num) {
+            while (k > 0 && !s.empty() && s.back() > c) {
+                s.pop_back();
+                k--;
+            }
+            s.push_back(c);
+        }
+
+        
+        s.resize(s.length() - k);
+        
+        for(i=0;i<s.length();i++)
+        {
+            if(s[i]!='0')
+            {
+                break;
+            }
+        }
+        
+        s=s.substr(i,s.length()-i);
+        
+        if(s.empty())
+            s="0";
+        
+        return s;
+    }
+};