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JavaScript Program to Find a triplet that sum to a given value
We are going to write a JavaScript program to find a triplet that sum up to a given value. This program will make use of nested loops to iterate over the input array and check for the existence of a triplet with a sum equal to the given value. Our program will continuously search for a triplet until it is found or all possible combinations have been exhausted. This program will make it possible for us to find a triplet that sum up to a given value in an efficient and straightforward manner.
Approach
The approach to find a triplet that sums up to a given value can be achieved using the following steps −
Sort the input array in ascending order.
Loop through the array and fix one element
Initialize two pointers, one pointing to the next element of the fixed element, and the other pointing to the end of the array.
Check if the sum of the three elements is equal to the given value.
If the sum is less than the given value, increment the left pointer.
If the sum is greater than the given value, decrement the right pointer. Repeat the process until either a triplet is found or the pointers cross each other.
Example
Given an array of integers, we want to find a triplet that sum to a given value. Here's a JavaScript program that solves this problem −
function findTriplet(arr, sum) {
// First, we sort the array in ascending order
arr.sort((a, b) => a - b);
// Next, we iterate through the array with the outer loop
for (let i = 0; i < arr.length - 2; i++) {
// We start the inner loop from i + 1 to avoid using the same number twice
let left = i + 1;
let right = arr.length - 1;
// The inner loop moves the left and right pointers towards each other
while (left < right) {
// If the sum of the current triplet is equal to the given sum, we have found our solution
if (arr[i] + arr[left] + arr[right] === sum) {
return [arr[i], arr[left], arr[right]];
}
// If the sum of the current triplet is less than the given sum, we need to increase the sum
// So, we move the left pointer to the right
else if (arr[i] + arr[left] + arr[right] < sum) {
left++;
}
// If the sum of the current triplet is greater than the given sum, we need to decrease the sum
// So, we move the right pointer to the left
else {
right--;
}
}
}
// If no triplet is found, we return null
return null;
}
// Example usage
let arr = [1, 4, 45, 6, 10, 8];
let sum = 22;
let triplet = findTriplet(arr, sum);
console.log(triplet);
Explanation
The function findTriplet takes in an array arr and a sum as arguments.
First, the array is sorted in ascending order using the sort method.
Next, we iterate through the array with the outer loop, using for loop with the variable i starting from 0 to arr.length - 2.
Within the outer loop, we start the inner loop from i + 1 to avoid using the same number twice. Two pointers left and right are initialized with i + 1 and arr.length - 1, respectively.
In the inner loop, we use a while loop to keep moving the left and right pointers towards each other until left is less than right.
Within the while loop, we check the current sum of the triplet arr[i] + arr[left] + arr[right].
If it's equal to the given sum, we have found our solution and we return the triplet [arr[i], arr[left], arr[right]].
If it's less than the given sum, we need to increase the sum, so we move the left pointer to the right by incrementing left.
If it's greater than the given sum, we need to decrease the sum
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