1899. Merge Triplets to Form Target Triplet

Problem

Tags: Array, Greedy

A triplet is an array of three integers. You are given a 2D integer array triplets, where triplets[i] = [ai, bi, ci] describes the i^th triplet. You are also given an integer array target = [x, y, z] that describes the triplet you want to obtain.

To obtain target, you may apply the following operation on triplets any number of times (possibly zero):

• Choose two indices (0-indexed) i and j (i != j) and update triplets[j] to become [max(ai, aj), max(bi, bj), max(ci, cj)].
  • For example, if triplets[i] = [2, 5, 3] and triplets[j] = [1, 7, 5], triplets[j] will be updated to [max(2, 1), max(5, 7), max(3, 5)] = [2, 7, 5].

Return true if it is possible to obtain the target triplet [x, y, z] as an element of triplets, or false otherwise.

Example 1:

Input: triplets = [[2,5,3],[1,8,4],[1,7,5]], target = [2,7,5]
Output: true
Explanation: Perform the following operations:
- Choose the first and last triplets [[2,5,3],[1,8,4],[1,7,5]]. Update the last triplet to be [max(2,1), max(5,7), max(3,5)] = [2,7,5]. triplets = [[2,5,3],[1,8,4],[2,7,5]]
The target triplet [2,7,5] is now an element of triplets.

Example 2:

Input: triplets = [[3,4,5],[4,5,6]], target = [3,2,5]
Output: false
Explanation: It is impossible to have [3,2,5] as an element because there is no 2 in any of the triplets.

Example 3:

Input: triplets = [[2,5,3],[2,3,4],[1,2,5],[5,2,3]], target = [5,5,5]
Output: true
Explanation: Perform the following operations:
- Choose the first and third triplets [[2,5,3],[2,3,4],[1,2,5],[5,2,3]]. Update the third triplet to be [max(2,1), max(5,2), max(3,5)] = [2,5,5]. triplets = [[2,5,3],[2,3,4],[2,5,5],[5,2,3]].
- Choose the third and fourth triplets [[2,5,3],[2,3,4],[2,5,5],[5,2,3]]. Update the fourth triplet to be [max(2,5), max(5,2), max(5,3)] = [5,5,5]. triplets = [[2,5,3],[2,3,4],[2,5,5],[5,5,5]].
The target triplet [5,5,5] is now an element of triplets.

Constraints:

• 1 <= triplets.length <= 10^5
• triplets[i].length == target.length == 3
• 1 <= ai, bi, ci, x, y, z <= 1000

Code

JS

// 1899. Merge Triplets to Form Target Triplet (6/17/53418)
// Runtime: 220 ms (38.89%) Memory: 69.85 MB (59.26%) 

/**
 * @param {number[][]} triplets
 * @param {number[]} target
 * @return {boolean}
 */
var mergeTriplets = function(triplets, target) {
    const n = triplets.length;
    let s = [0,0,0];
    for(let i = 0; i < 3; i++) {
        for(let p = 0; p < n; p++) {
            if(triplets[p][i] === target[i]) {
                let f = true;
                for(let j = 0; j < 3; j++) {
                    if(i === j) continue;
                    if(triplets[p][j] > target[j]) f = false;
                }
                if(f) s = [Math.max(s[0], triplets[p][0]), Math.max(s[1], triplets[p][1]), Math.max(s[2], triplets[p][2])];
                else continue;
                if(s[0] === target[0] && s[1] === target[1] && s[2] === target[2]) return true;
            }
        }
    }
    
    return false;
};