82 lines
1.9 KiB
JavaScript
82 lines
1.9 KiB
JavaScript
/**
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* Get index with specific start index one by one. e.g.
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* min: 3, max: 9, start: 6
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*
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* Return index is:
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* [0]: 6
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* [1]: 7
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* [2]: 5
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* [3]: 8
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* [4]: 4
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* [5]: 9
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* [6]: 3
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*/
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export function getIndexByStartLoc(min, max, start, index) {
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const beforeCount = start - min;
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const afterCount = max - start;
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const balanceCount = Math.min(beforeCount, afterCount) * 2;
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// Balance
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if (index <= balanceCount) {
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const stepIndex = Math.floor(index / 2);
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if (index % 2) {
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return start + stepIndex + 1;
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}
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return start - stepIndex;
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}
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// One is out of range
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if (beforeCount > afterCount) {
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return start - (index - afterCount);
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}
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return start + (index - beforeCount);
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}
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/**
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* We assume that 2 list has only 1 item diff and others keeping the order.
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* So we can use dichotomy algorithm to find changed one.
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*/
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export function findListDiffIndex(originList, targetList, getKey) {
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const originLen = originList.length;
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const targetLen = targetList.length;
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let shortList;
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let longList;
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if (originLen === 0 && targetLen === 0) {
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return null;
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}
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if (originLen < targetLen) {
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shortList = originList;
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longList = targetList;
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} else {
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shortList = targetList;
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longList = originList;
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}
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const notExistKey = { __EMPTY_ITEM__: true };
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function getItemKey(item) {
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if (item !== undefined) {
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return getKey(item);
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}
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return notExistKey;
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}
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// Loop to find diff one
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let diffIndex = null;
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let multiple = Math.abs(originLen - targetLen) !== 1;
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for (let i = 0; i < longList.length; i += 1) {
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const shortKey = getItemKey(shortList[i]);
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const longKey = getItemKey(longList[i]);
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if (shortKey !== longKey) {
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diffIndex = i;
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multiple = multiple || shortKey !== getItemKey(longList[i + 1]);
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break;
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}
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}
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return diffIndex === null ? null : { index: diffIndex, multiple };
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}
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