LeetCode 旋转数组算法题解 All In One

js / ts 实现螺旋数组

旋转原理图解

  // 交换
  function swapArray(i, j, nums) {
    while(i < j) {
      [
        nums[i],
        nums[j]
      ] = [
        nums[j],
        nums[i]
      ];
      // console.log(`nums[${i}] =`, nums);
      i++;
      j--;
    }
  }
  // 旋转
  function rotateArray(k, nums) {
    const len = nums.length;
    // 1. 交换 (len - 1) / 2 次
    swapArray(0, len - 1, nums);
    // 2. 交换 (k - 1) / 2 次
    swapArray(0, k - 1, nums);
    // 3. 交换 Math.ceil((len - 1 - k) / 2) 次
    swapArray(k, len - 1, nums);
  }

189. Rotate Array

"use strict";

/**
 *
 * @author xgqfrms
 * @license MIT
 * @copyright xgqfrms
 * @created 2022-08-10
 * @modified
 *
 * @description 89. Rotate Array
 * @description 189. 旋转数组
 * @difficulty Medium
 * @ime_complexity O(n)
 * @space_complexity O(n)
 * @augments
 * @example
 * @link https://leetcode.com/problems/rotate-array/
 * @link https://leetcode-cn.com/problems/rotate-array/
 * @solutions
 *
 * @best_solutions
 *
 */

export {};

const log = console.log;

/**
 Do not return anything, modify nums in-place instead.
 */

// solution 2: in-place 就地交换算法 ✅
function reverse(i: number, j: number, nums: number[]): void {
  while(i < j){
    [
      nums[i],
      nums[j]
    ] = [
      nums[j],
      nums[i]
    ];
    // 两两互换
    i++;
    j--;
  }
};

function rotate(nums: number[], k: number): void {
  k %= nums.length;
  // 如果 k 大于 nums.length 则完成一个循环，这意味着它将保持不变，我们必须进行剩余移位
  // reverse all
  reverse(0, nums.length-1, nums);
  // reverse first part
  reverse(0, k - 1, nums)
  // reverse second part
  reverse(k, nums.length-1, nums);
};


// type alias
type ObjectType = {
  // input: any[];
  input: [number[], number];
  result: number[];
  desc: string;
}

// 1. TypeScript & define Object Array Interface methods ✅ extends Array<ObjectType>
// interface TestCaseInterface extends Array<ObjectType> {
//   //
// }

// 2. TypeScript & define Object Array Interface methods ✅ [index: number]: ObjectType;
interface TestCaseInterface extends Array<any> {
  [index: number]: ObjectType;
}

// 测试用例 test cases
const testCases: TestCaseInterface = [
  {
    input: [
      [1,2,3,4,5,6,7],
      3,
    ],
    result: [5,6,7,1,2,3,4],
    desc: 'value equal to [5,6,7,1,2,3,4]',
  },
  {
    input: [
      [-1,-100,3,99],
      2,
    ],
    result: [3,99,-1,-100],
    desc: 'value equal to [3,99,-1,-100]',
  },
];
for (const [i, testCase] of testCases.entries()) {
  const [first, second] = testCase.input;
  rotate(first, second);
  log(`test case i result: \n`, first.join('') === testCase.result.join('') ? `passed ✅` : `failed ❌`, testCase.result);
}


// solution 1:暴力破解：❌ Time Limit Exceeded
// function rotate(nums: number[], k: number): void {
//   if(k === 0) {
//     // return;
//   } else {
//     const len = nums.length;
//     while(k > 0) {
//       // deep clone
//       let temp = [];
//       for(let i= 0; i< len; i++) {
//         // 破解对象引用 bug, 值引用
//         temp[i] = nums[i];
//       }
//       let end = temp[len - 1];
//       // 循环队列
//       for(let i = 1; i< len; i++) {
//         // 交换swap
//         nums[i] = temp[i - 1];
//       }
//       nums[0] = end;
//       // console.log(`nums =`, nums);
//       k -= 1;
//     }
//   }
//  // no return, in-place 就地交换
// };

https://leetcode.com/problems/rotate-array/
https://leetcode.cn/problems/rotate-array/