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969.煎饼排序.js
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969.煎饼排序.js
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/*
* @lc app=leetcode.cn id=969 lang=javascript
*
* [969] 煎饼排序
*/
// @lc code=start
// 翻转数组前n位,并且更新idx列表
const reverse = (arr, n, idxList) => {
for (let i = 0, j = n - 1; i < j; i++, j--) {
const t = arr[j];
arr[j] = arr[i];
arr[i] = t;
idxList[arr[i]] = i;
idxList[arr[j]] = j;
}
};
/**
* @param {number[]} arr
* @return {number[]}
*/
var pancakeSort = function (arr) {
const ret = [];
const idxList = new Array(arr.length + 1);
for (let i = 0; i < arr.length; i++) idxList[arr[i]] = i;
for (let i = arr.length; i >= 1; i--) {
if (idxList[i] === i - 1) continue;
if (idxList[i] + 1 !== 1) {
ret.push(idxList[i] + 1); // 翻转元素值从1开始
reverse(arr, idxList[i] + 1, idxList);
}
if (i !== 1) {
ret.push(i);
reverse(arr, i, idxList);
}
}
return ret;
};
// @lc code=end