31 lines
876 B
JavaScript
31 lines
876 B
JavaScript
// https://www.freecodecamp.org/learn/coding-interview-prep/algorithms/pairwise
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function pairwise(arr, sum) {
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const arr2 = arr.map((num, index) => ({ num: num, index: index }));
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arr2.sort(({ num: numA, index: indexA }, { num: numB, index: indexB }) => {
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if (numA === numB) {
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return indexA - indexB;
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} else {
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return numA - numB;
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}
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});
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let [i, reverseI, pairsIndexSum] = [0, arr2.length - 1, 0];
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while (i < reverseI) {
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if (arr2[i].num + arr2[reverseI].num === sum) {
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if (arr2[i].num === arr2[reverseI].num) {
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pairsIndexSum += arr2[i++].index + arr2[i++].index;
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} else {
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pairsIndexSum += arr2[i++].index + arr2[reverseI--].index;
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}
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} else if (arr2[i].num + arr2[reverseI].num < sum) {
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i++;
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} else {
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reverseI--;
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}
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}
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return pairsIndexSum;
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}
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console.log(pairwise([1, 1, 1], 2));
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