Codility - NumberOfDiscIntersections


We draw N discs on a plane. The discs are numbered from 0 to N − 1. An array A of N non-negative integers, specifying the radiuses of the discs, is given. The J-th disc is drawn with its center at (J, 0) and radius A[J].
We say that the J-th disc and K-th disc intersect if J ≠ K and the J-th and K-th discs have at least one common point (assuming that the discs contain their borders).
The figure below shows discs drawn for N = 6 and A as follows:
A[0] = 1
A[1] = 5
A[2] = 2
A[3] = 1
A[4] = 4
A[5] = 0

There are eleven (unordered) pairs of discs that intersect, namely:
discs 1 and 4 intersect, and both intersect with all the other discs;
disc 2 also intersects with discs 0 and 3.
Write a function:
function solution(A);
that, given an array A describing N discs as explained above, returns the number of (unordered) pairs of intersecting discs. The function should return −1 if the number of intersecting pairs exceeds 10,000,000.
Given array A shown above, the function should return 11, as explained above.
Write an efficient algorithm for the following assumptions:
N is an integer within the range [0..100,000];
each element of array A is an integer within the range [0..2,147,483,647].
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  • 座標値のLeft値に準じ、範囲に属する場合はカウントします.(50%)
  • function solution(A) {
        let answer = new Set();
        let pair = [];
       A.map((ele, idx) => {
           let left = idx - ele;
           let right = idx + ele;
           pair.push({left: left, right: right});
       })
    
       pair.map((ele, idx) => {
           let current = ele;
    
           for (let j=0; j<pair.length; j++) {
               if (idx !== j) {
                   if ((pair[j].left <= current.left && current.right <= pair[j].right)
                        || (current.left <= pair[j].left && pair[j].left <= current.right)) {
                    
                    let temp = idx + "/" + j;
                    let reverse = j + "/" + idx;
                    if (!answer.has(reverse)) {
                        answer.add(temp);
                    }
                   } 
               } else {
                   continue;
               }
           }
       });
       return (answer.size > 10000000) ? -1 : answer.size;
    }
  • 座標値のRight値がLeft値以上である場合、カウント(100%)
  • を増加する.
    function solution(A) {
        let pair = [];
       for(let i=0; i<A.length; i++){
            pair.push({l:i-A[i],r:i+A[i]});
        }
        
        pair.sort((a,b)=>a.l-b.l);
    
        let answer=0;
        for (let i=0; i<pair.length; i++) {
            for (let j=i+1; j<pair.length; j++) {
                if (pair[i].r >= pair[j].l) {
                    answer++
                
                } else {
                    break
                }
    
                if(answer > 10000000) return -1
            }
        }
       return answer
    }