randomized

本文介绍了randomized_quicksort的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

这code没有告诉我任何输出

this code does not show me any output

#include <cstdlib> #include <iostream> using namespace std; int partition(int a[], int left, int right) { int i = left; int j = right; int temp; int pivot = a[left]; while(i <= j) { while(a[i] < pivot) i++; while(a[j] > pivot) j--; if(i>j) break; if (i<j){ temp = a[i]; a[i] = a[j]; a[j] = temp; i++; j--; } } return i; } int randomized_partition(int a[], int left, int right){ int t = left + rand() % (right - left + 1); std::swap(a[right], a[t]); return partition(a, left, right); } void randomized_quicksort(int a[], int l, int r){ if(l> = r) return; int q = randomized_partition(a, l, r); randomized_quicksort(a, l, q-1); randomized_quicksort(a, q+1, r); } int main(){ int a[] = {12, 6, 4, 7, 9, 10, 11, 14, 13, 19, 18, 21, 20}; int n = sizeof(a) / sizeof(n); randomized_quicksort(a, 0, n-1); for (int i = 0; i < n; i++){ cout << a[i] << " " << endl; } return 0; }

这是randomized_quicksort从引进算法第三版，请您帮

it is randomized_quicksort from introduction in algorithms third edition and please help

推荐答案

该计划被卡在调用分区（2,4）。数组的相关部分是 6，9，7 的时间，所以透视获取初始化为 6 。

The program gets stuck in the call to partition(2, 4). The relevant part of the array is 6, 9, 7 at the time, so pivot get initialized to 6.

您进入主，而循环，而我循环立即终止，因为它总是在第一时间各地，因为 A [1] ==透视。所以，你输入Ĵ循环，执行两次，因为 7 和 9 都比透视，这是更大的 6 。该Ĵ循环结束时，Ĵ== 2 ，因为 A [J] ==透视。

You enter the main while loop, and the i loop terminates immediately, as it always does the first time around, because a[i] == pivot. So you enter the j loop, which executes twice because 7 and 9 are both greater than pivot, which is still 6. The j loop terminates when j == 2 because a[j] == pivot.

移动以来，第一个条件是假，因为我不大于更大Ĵ 。第二个条件是假，因为我不大于Ĵ少。这标志着主，而循环结束，所以我们检查循环的条件，并发现它的真，因为我等于Ĵ。我们没有改变任何数组元素的值，因此内，而回路永远不会再运行，并且条件语句仍然假。你陷在一个无限循环，永远不会取得任何进展。

Moving along, the first conditional is false because i is not greater than j. The second conditional is false because i is not less than j. That marks the end of the main while loop, so we check the loop's condition and find that it's true because i is equal to j. We haven't changed any of the array elements' values, so the inner while loops never run again, and the conditionals remain false. You get stuck in an infinite loop, never making any progress.

快来看看你的教科书。无论是有书中的错误，或者你犯了一个错误抄录吧。

Take a closer look at your textbook. Either there's a mistake in the book, or you made a mistake transcribing it.