challenge(DP): get min spaces in Pi

Author: dushimsam

algo-expert-premium/dynammic_programming/numbers_in_pi.cpp

@@ -0,0 +1,71 @@
+#include <bits/stdc++.h>
+using namespace std;
+typedef unordered_map<int, int> mp;
+
+int getMinSpaces(string pi, set<string> numbersTable, mp &cache, int idx)
+{
+ // return -1 if the number on which we called this fn was the last one
+ if (idx == pi.length())
+ return -1;
+ // check if the value for this particular idx already exists in the cache, so that we don't make unnecessary repetition
+ if (cache.find(idx) != cache.end())
+ return cache.at(idx);
+ // declare the minSpaces variable for this particular idx
+ int minSpaces = INT_MAX;
+ // iterate from this current idx to the end, trying to minimize the space
+ for (int i = idx; i < pi.length(); i++)
+ {
+ // create a prefix - from this idx back to the end
+ string prefix = pi.substr(idx, i + 1 - idx);
+ // check if the prefix exists in the set 'numbersTable'
+ if (numbersTable.find(prefix) != numbersTable.end())
+ {
+ // reduce the existing spaces
+ int minSpacesInSuffix = getMinSpaces(pi, numbersTable, cache, i + 1);
+
+ // Handle int overflow
+ if (minSpacesInSuffix == INT_MAX)
+ {
+ minSpaces = min(minSpacesInSuffix, minSpaces);
+ }
+ else
+ {
+ minSpaces = min(minSpaces, minSpacesInSuffix + 1);
+ }
+ }
+ }
+ // insert the min spaces for this idx
+ cache.insert({idx, minSpaces});
+ // return the min spaces for the idx
+ return cache.at(idx);
+}
+
+int numbersInPi(string pi, vector<string> numbers)
+{
+ // create the set to store the numberse
+ set<string> numbersTable;
+ // insert numbers in the set
+ for (string num : numbers)
+ {
+ numbersTable.insert(num);
+ }
+ mp cache;
+ // lead numbers from the back to the front
+ for (int i = pi.length() - 1; i >= 0; i--)
+ {
+ // for each number fill up the minSpaces for it. by Calling getMinSpaces function
+ getMinSpaces(pi, numbersTable, cache, i);
+ }
+ // return the minSpaces from the cache located at 0' index
+ return cache.at(0) == INT_MAX ? -1 : cache.at(0);
+}
+
+int main()
+{
+
+ string pi = "3141592653589793238462643383279";
+ vector<string> nums = {"314159265358979323846", "26433", "8", "3279", "314159265", "35897932384626433832", "79"};
+ // Expected result - 2
+ cout << numbersInPi(pi, nums) << endl;
+ return 0;
+}