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Technical articles with clear explanations and examples

Remove Invalid Parentheses in C++

Arnab Chakraborty
Arnab Chakraborty
Updated on 11-Mar-2026 429 Views

Suppose we have a string of parentheses. We have to remove minimum number of invalid parentheses and return the well formed parentheses strings, So if the input is like “()(()()”, so the result will be [“()()()”, “()(())”]To solve this, we will follow these steps −Define a method called solve(), this will take pos, left, right, l, r, string array res and string temp.if pos is same as size of s, then, if left is same as 0 and right is same as 0, then, if (m[temp] is non-zero) is false, then, insert temp at the end of resm[temp] := 1returnif ...

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Burst Balloons in C++

Arnab Chakraborty
Arnab Chakraborty
Updated on 11-Mar-2026 532 Views

Suppose we have n balloons, these are indexed from 0 to n-1. Here each balloon is painted with a number on it represented by one array called nums. we have to burst all the balloons. If we burst balloon i we will get nums[i – 1] * nums[i] * nums[i + 1] number of coins. After the burst, the i – 1 and i + 1 then becomes adjacent. We have to find the maximum coins to collect by bursting the balloons wisely.So if the input is like [3, 1, 5, 7], then the result will be 148. Initially the ...

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Count of Smaller Numbers After Self in C++

Arnab Chakraborty
Arnab Chakraborty
Updated on 11-Mar-2026 502 Views

Suppose we have an array nums, we have to find another array called count, in this count array, the count[i] stores the number of smaller elements to the right of nums[i].So if the input is like: [5, 2, 7, 1], then the result will be [2, 1, 1, 0].To solve this, we will follow these steps −Define one method called update(), this will take index, array bit and nwhile index 0, do −ans = ans + bit[index]index = index – (index AND - index)return ansFrom the main method, do the following −n := size of numsDefine an array res ...

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Remove Duplicate Letters in C++

Arnab Chakraborty
Arnab Chakraborty
Updated on 11-Mar-2026 251 Views

Suppose we have a string consisting of only lowercase letters. We have to remove all duplicate letters such that all letters only occur once. And we have to display the result in the smallest lexicographic sequence. So if the input is like “abccb”, then the result will be “abc”To solve this, we will follow these steps −ans := one empty stringDefine one stack stDefine an array onStack of size 26Define one map mn := size of sfor initializing i := 0, when i < n, increase i by 1 do −increase m[s[i]] by 1for initializing i := 0, when i ...

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Patching Array in C++

Arnab Chakraborty
Arnab Chakraborty
Updated on 11-Mar-2026 430 Views

Suppose we have an array nums and one number. We can add elements in the array, such that any number in range [1, n] (both are inclusive) can be formed by the sum of some elements in the array. We have to find the minimum number of required patches. So when the array is like [1, 4] and given number is n = 7, then output will be 1, as initially the nums are [1], [4] and [1, 4] = 5, now if we add 2 into array, then the nums will be [1], [2], [4], [1, 2], [1, 4], ...

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Self Crossing in C++

Arnab Chakraborty
Arnab Chakraborty
Updated on 11-Mar-2026 351 Views

Suppose we have an array x of n numbers. We start at point (0, 0) and moves x[0] units to the north direction, then x[1] units to the west direction, x[2] units to the south direction , x[3] units to the east direction and so on. In other words, after each move our direction changes counter-clockwise. We have to devise an one-pass algorithm with O(1) extra space to determine whether our path crosses itself, or not.So if the array is like − [3, 4, 2, 5]Answer will be true.To solve this, we will follow these steps −insert 0 at the ...

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Data Stream as Disjoint Intervals in C++

Arnab Chakraborty
Arnab Chakraborty
Updated on 11-Mar-2026 301 Views

Suppose we have a data stream input of integers, these are like a1, a2, ..., an, ..., we have to summarize the numbers seen so far as a list of disjoint intervals. For example, suppose the input integers are 1, 3, 8, 2, 7, ..., then the summary will be −[1, 1][1, 1], [3, 3][1, 1], [3, 3], [8, 8][1, 3], [8, 8][1, 3], [7, 8].To solve this, we will follow these steps −Make a set called numsin the initializer, set low := -inf and high := infFrom the addNum method that takes num as input, insert num into the ...

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Program to find Star number in C++

Ayush Gupta
Ayush Gupta
Updated on 11-Mar-2026 238 Views

In this problem, we are given a number n. Our task is to create a program to find Star number in C++.Star Number is a special number that represents a centered hexagram (sixpoint star).Some start numbers are 1, 13, 37, 73, 121.Let’s take an example to understand the problemInputn = 5Output121Solution ApproachTo find the nth star number we will use the formula.Let’s see the general formula for the star number.n = 2 -> 13 = 12 + 1 = 6(2) + 1 n = 3 -> 37 = 36 + 1 = 6(6) + 1 n = 4 -> 73 ...

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Program to find sum of 1 + x/2! + x^2/3! +...+x^n/(n+1)! in C++

Ayush Gupta
Ayush Gupta
Updated on 11-Mar-2026 377 Views

In this problem, we are given two values x and n that corresponds to the given series. Our task is to create a program to find sum of 1 + x/2! + x^2/3! +…+x^n/(n+1)! in C++.Problem description − we need to find the sum of series based on the given values of x and n. In the series, every other term differs from the previous term by x/i for ith term.Let’s take an example to understand the problemInputx = 6, n = 4Output29.8ExplanationThe sum of the series is1 + 6/2 + 36/6 + 216/24 + 1296/120 = 29.8Solution ApproachTo find ...

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Program to find Sum of a Series a^1/1! + a^2/2! + a^3/3! + a^4/4! +.......+ a^n/n! in C++

Ayush Gupta
Ayush Gupta
Updated on 11-Mar-2026 686 Views

In this problem, we are given two numbers a and n. Our task is to create a program to find Sum of a Series a^1/1! + a^2/2! + a^3/3! + a^4/4! +…….+ a^n/n! in C++.Problem description − The problem is to find the sum of the given series using the given values of a and n. The series is a special series in which each term is the multiple of the last term with a/i, i -> 1 to n.Let’s take an example to understand the problemInputa = 3, n = 4Output15.375Explanationsum of series is(3^1)/1! + (3^2)/2! + (3^3)/3! + ...

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