next函数为求str字典序的下一项,lexicographic函数为求str字典序的第n项

Lexicographic order.js

"use strict";

function next (str) {
  const charArr = str.split('');
  const charReverseArr = charArr.reverse();

  const inflectionIndex = charReverseArr.findIndex((element, index, array) => element < array[index - 1]);


  const right = charReverseArr.slice(0, inflectionIndex);
  const inflection = charReverseArr[inflectionIndex];
  const left = charReverseArr.slice(inflectionIndex + 1, charReverseArr.length);

  // %>_<%
  right.sort((a, b) => a > b);
  const replaceIndex = right.findIndex(element => element > inflection);

  const newInFlection = right.splice(replaceIndex, 1, inflection);

  const concat = right.reverse().concat(newInFlection, left);
  const result = concat.reverse().join('');
  return result;
}
/**
 *
 */
function lexicographic (str, nextTrick) {
  if (nextTrick === 0) {
    console.log(str);
  } else {
    lexicographic(next(str), nextTrick - 1);
  }
}

var now = '123456789'
for (let i = 1; i < 2014; i++) {
  now = next(now);
}
console.log(now);
// 向后推演2013次, 得到第2014个字典序
lexicographic('123456789', 2013);

next函数为求str字典序的下一项
lexicographic函数为求str字典序的第n项