如何找到在JavaScript中按降序对数字数组进行排序所需的最小交换次数

Question

我正在尝试获取我的代码来做到这一点：

原始数组= [1,2,3,4]交换一次-> [4,2,3,1]再次交换-> [4,3,2,1]

因此结果为2

但是它不起作用。这是我到目前为止的内容：

   

 function check(arr){
	var sarr = [];
	var cnt = 0;
	var arrL = arr.length;
   // Create a second copy of the array for reference
	var arrCopy = [...arr];
	for(let i=0; i<arrL;i++){
		var maxV = Math.max(...arr);
		sarr.push(maxV);
		let pos = arr.indexOf(maxV);
		// Remove the found number
		arr.splice(pos,1);
		// Check if the index of the number in the new array is same with the copy, if not then there was a swap
		let ai =arrCopy.indexOf(maxV); 
		let si =sarr.indexOf(maxV);
		if (ai !== si && (i+1)!=arrL && pos !== 0){
		cnt++;
        };
	}

	console.log(cnt);
}

check([1, 2, 3, 4, 5, 6]);//Result should be 3
check([6,5,4,3,2,1]); //result should be 0

check([1,2,3,4]); //result should be 2

check([1,3,2,5,4,6]); //result should be 3

check([1,2,10,4,5,6,7,8,9,3,12,11]);//result should be 6

check([ 49, 37, 9, 19, 27, 3, 25, 11, 53,  42, 57, 50, 55,  56, 38, 48, 6, 33, 28, 8, 20, 31, 51, 14, 23, 4, 58, 52, 36, 22, 41, 47, 39, 2, 7, 13, 45, 1, 44, 32, 10, 15, 21, 30, 17,  60, 29, 5, 59, 12, 40, 24, 54, 46, 26, 43, 35, 34, 18, 16]);//result should be 54

有人可以让我知道我在做什么错吗？

Answer 1

我将从降序排列的数组开始，以获得正确的项目索引。

出于实际原因（或者只是循环的较短概念，包括检查和减量），我从数组末尾开始循环。

然后，我在dame索引处检查array和reversed的值，然后继续进行迭代。

如果值不相同，则会交换所需位置i和实际位置p上的项目，并增加计数。

最后返回计数。

function check(array) {
  var reversed = array.slice().sort((a, b) => b - a),
      count = 0,
      i = array.length,
      p;

  while (i--) {
      if (array[i] === reversed[i]) continue;
      p = array.indexOf(reversed[i]);
      [array[i], array[p]] = [array[p], array[i]];
      count++;
  }
  console.log(...array);
  return count;
}

console.log(check([1, 2, 3, 4, 5, 6])); // 3
console.log(check([6, 5, 4, 3, 2, 1])); // 0
console.log(check([1, 2, 3, 4])); // 2
console.log(check([1, 3, 2, 5, 4, 6])); // 3
console.log(check([1, 2, 10, 4, 5, 6, 7, 8, 9, 3, 12, 11])); // 6
console.log(check([ 49, 37, 9, 19, 27, 3, 25, 11, 53,  42, 57, 50, 55,  56, 38, 48, 6, 33, 28, 8, 20, 31, 51, 14, 23, 4, 58, 52, 36, 22, 41, 47, 39, 2, 7, 13, 45, 1, 44, 32, 10, 15, 21, 30, 17,  60, 29, 5, 59, 12, 40, 24, 54, 46, 26, 43, 35, 34, 18, 16])); // 54

.as-console-wrapper { max-height: 100% !important; top: 0; }

Answer 2

function minimumSwaps(arr) {
  var count = 0;
  arr.sort((a, b) => {
    if (a < b) {
      count++;
    }
  });
  return count;
}

console.log(minimumSwaps([1, 2, 3, 4, 7, 6, 5]));