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README.md

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Cheat Sheet

| Important functions| | Manipulation Algorithm | | String important functions | | Sets | | Maps |

Important functions

Sorting

  1. sort(arr,arr+n) : quick sort in (nlogn) ascending order.
  2. sort(arr,arr+n,greater()) : sort in descending order.
  3. sort(arr,arr+n, comparable) : sort accordingly.
	bool comparable(int a, int b)
	{
		return a>b;
	}

Reverse

reverse(arr,arr+n);

Max element in vector

*max_element(arr,arr+n);

Min element

*min_element(arr,arr+n);

Finding sum of all elements in vector

accumulate(arr,arr+n,0) : 0 is to specify the initial value of sum

Count of pattern in vector

count(arr,arr+n);

Finding the iterator position of the patter in vector

find(arr,arr+n,pattern); return iterator to first match else vector.end() if not found

Shifting the vector

rotate(arr.begin(), arr.begin()+3, arr.end()); the element at 3rd position become the first after first rotate. rotate(arr.begin(), arr.end() + (arr.size() - 3), arr.end()); the element at 3rd position become the first after last 3rd rotate.

value not less than x

lower_bound(arr,arr+n,x);

value not greater than x

upper_bound(arr,arr+n,x);

Common elements in set

set_intersection(vec1.begin(),vect1.end(),vec2.begin(),vect2.end(), result.begin()) : store the common elements in result vector

All elements in set

set_union(vec1.begin(),vect1.end(),vec2.begin(),vect2.end(), result.begin()) : store the all elements in result vector

Manipulation Algorithm

Erase

arr.erase(iteratorPosition) : erases the element at position +1 arr.erase(unique(arr.begin(),arr.end()), arr.end()) : erases the duplicate elements.

Permutation

  1. next_permutation(arr,arr+n);
  2. prev_permutation(arr,arr+n);

String important functions

find

  1. str.find_last_of("pattern") :returns substring index position of the match from the last
  2. str.find_first_of("pattern") : returns substring index position of the match from the beginning
  3. str.find("pattern"): return position of the patterns first match else return -1;

sub-string

  1. str.substr(position) : return sub-string from that position to the last.
  2. str.substr(indexPosition, substringLength) : return sub-string from that position to the sub-string length specified.

Sets

set<int,greater> setName; : stores element in descending order. set.insert(10);

Copying values in set from vector

set setName(arr.begin(),arr.end())

Find

setName.find(30) : return iterator position else return setName.end()

Erase a value

  1. setName.erase(value)
  2. setName.erase(arr.begin(),arr.end(), setName.find(30) )

Count fn to check if element is present or not

setName.count(element) : // return 1 if present or 0 when not present.

Maps

  1. map<int,int> mapName;
  2. mapName.insert(pair<int,int>(10,40));
  3. itrPos->first : gives key
  4. itrPos->second : gives value

Modifying value pair

mapName.find(keyValue)->second = newValue;