学习算法 javascript 实现，写一个简单的快速排序，在浏览器中一直报错。代码：
function quickSort(arr){ var len;
len=arr.length; if (len <= 1) { return arr; //如果数组只有一个数，就直接返回；
} var midlen = Math.floor(len/2); var mid = arr[midlen]; // console.log(mid);
var left = []; var right = []; for (var i = 0; i < len; i++) { if (arr[i] < mid) {
left.push(arr[i]);
} else {
right.push(arr[i]);
}
} // console.log(left.concat([mid],right));
return quickSort(left).concat([mid], quickSort(right));
} //test
console.log(quickSort([9, 2, 8, 5, 1]));
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javascript Quick sort No error, where did I go wrong? -PHP Chinese website Q&A-javascript quick sort No error, where did I go wrong? -PHP Chinese website Q&A
Let’s take a look and learn.
死循环，堆栈溢出了。right数组有两项，9，8.递归执行的时候始终是9，8.
因为此时mid是8，ara[i]始终>=mid,right数组始终是9，8.就死循环了。
正确写法如下：
function quickSort(arr){ var len; len=arr.length; if (len <= 1) { return arr; //如果数组只有一个数，就直接返回； } var midlen = Math.floor(len/2); // var mid = arr[midlen]; var mid = arr.splice(midlen,1)[0]; // console.log(mid); var left = []; var right = []; for (var i = 0,len=arr.length; i < len; i++) { if (arr[i] <= mid) { left.push(arr[i]); } else { right.push(arr[i]); } } // console.log(left.concat([mid],right)); return quickSort(left).concat([mid], quickSort(right)); }//testconsole.log(quickSort([9, 2, 8, 5, 1]));//输出：[ 1, 2, 5, 8, 9 ]