前言
本文整理并总结了十大经典的排序算法(冒泡排序、选择排序、插入排序、快速排序、归并排序、希尔排序、计数排序、基数排序、桶排序、堆排序)的时间复杂度、空间复杂度等性质。
本文并不会详细讲解每种排序算法的原理,网上有很多很好的教程,大家可以自己去搜了看。
最后我还亲自手写了十种排序算法的 c++ 代码,大家可以用来通过 LeetCode 912. 排序数组[1] 这道题。
性质汇总
如果发现图中有错误,请留言告知。
十大经典排序算法性质汇总
维基百科
我觉得还是英文维基百科讲的比较详细、严谨。如果大家看的比较累的话,可以自己百度搜索相应的教程。
冒泡排序
https://en.wikipedia.org/wiki/Bubble_sort
选择排序
https://en.wikipedia.org/wiki/Selection_sort
插入排序
https://en.wikipedia.org/wiki/Insertion_sort
快速排序
https://en.wikipedia.org/wiki/Quicksort
归并排序
https://en.wikipedia.org/wiki/Merge_sort
希尔排序
https://en.wikipedia.org/wiki/Shellsort
计数排序
https://en.wikipedia.org/wiki/Counting_sort
基数排序
https://en.wikipedia.org/wiki/Radix_sort
桶排序
https://en.wikipedia.org/wiki/Bucket_sort
堆排序
https://en.wikipedia.org/wiki/Heapsort
代码实现
所有的排序算法接口都是相同的,也就是 vector<int> xxxSort(vector<int>& nums)
。只需要你传入一个 vector<int>
类型的数组,就能返回排序后的结果。
运行下来可以发现,桶排序速度是比较快的。而冒泡排序、选择排序和插入排序因为时间复杂度太高无法通过本题,基数排序因为无法处理负数也不能通过本题。
class Solution { public: vector<int> sortArray(vector<int>& nums) { return quickSort(nums); } // 冒泡排序(超时) vector<int> bubbleSort(vector<int>& nums) { int n = nums.size(); for (int i = 0; i < n; ++i) { for (int j = n-2; j >= i; --j) { if (nums[j] > nums[j+1]) { swap(nums[j], nums[j+1]); } } } return nums; } // 选择排序(超时) vector<int> selectSort(vector<int>& nums) { int n = nums.size(); for (int i = 0; i < n; ++i) { int idx = i; for (int j = i; j < n; ++j) { if (nums[j] < nums[idx]) { idx = j; } } swap(nums[i], nums[idx]); } return nums; } // 插入排序(超时) vector<int> insertSort(vector<int>& nums) { int n = nums.size(); for (int i = 0; i < n; ++i) { for (int j = i; j > 0 && nums[j] < nums[j-1]; --j) { swap(nums[j], nums[j-1]); } } return nums; } // 快速排序(24 ms) void qSort(vector<int>& nums, int l, int r) { if (l >= r) return; int m = l; for (int i = l; i < r; ++i) { if (nums[i] < nums[r]) { swap(nums[m++], nums[i]); } } swap(nums[m], nums[r]); qSort(nums, l, m-1); qSort(nums, m+1, r); } vector<int> quickSort(vector<int>& nums) { int n = nums.size(); qSort(nums, 0, n-1); return nums; } // 归并排序(192 ms) vector<int> mSort(vector<int>& nums, int l, int r) { if (l >= r) return {nums[l]}; int m = l+(r-l)/2; vector<int> lnums = mSort(nums, l, m); vector<int> rnums = mSort(nums, m+1, r); vector<int> res; int i = 0, j = 0; while (i <= m-l && j <= r-m-1) { if (lnums[i] < rnums[j]) { res.push_back(lnums[i++]); } else { res.push_back(rnums[j++]); } } while (i <= m-l) { res.push_back(lnums[i++]); } while (j <= r-m-1) { res.push_back(rnums[j++]); } return res; } vector<int> mergeSort(vector<int>& nums) { int n = nums.size(); nums = mSort(nums, 0, n-1); return nums; } // 归并排序 + 非递归(80 ms) vector<int> mergeSortNR(vector<int>& nums) { int n = nums.size(); for (int len = 1; len < n; len <<= 1) { for (int l = 0; l < n-len; l += 2*len) { int m = l+len-1; int r = min(n-1, l+2*len-1); vector<int> res; int i = l, j = m+1; while (i <= m && j <= r) { if (nums[i] < nums[j]) { res.push_back(nums[i++]); } else { res.push_back(nums[j++]); } } while (i <= m) { res.push_back(nums[i++]); } while (j <= r) { res.push_back(nums[j++]); } for (int i = l; i <= r; ++i) { nums[i] = res[i-l]; } } } return nums; } // 希尔排序(40 ms) vector<int> shellSort(vector<int>& nums) { int n = nums.size(); for (int gap = n/2; gap > 0; gap /= 2) { for (int i = gap; i < n; ++i) { for (int j = i; j-gap >= 0 && nums[j-gap] > nums[j]; j -= gap) { swap(nums[j-gap], nums[j]); } } } return nums; } // 计数排序(32 ms) vector<int> countSort(vector<int>& nums) { int n = nums.size(); if (!n) return {}; int minv = *min_element(nums.begin(), nums.end()); int maxv = *max_element(nums.begin(), nums.end()); int m = maxv-minv+1; vector<int> count(m, 0); for (int i = 0; i < n; ++i) { count[nums[i]-minv]++; } vector<int> res; for (int i = 0; i < m; ++i) { for (int j = 0; j < count[i]; ++j) { res.push_back(i+minv); } } return res; } // 基数排序(不适用于负数) vector<int> radixSort(vector<int>& nums) { int n = nums.size(); int maxv = *max_element(nums.begin(), nums.end()); int maxd = 0; while (maxv > 0) { maxv /= 10; maxd++; } vector<int> count(10, 0), rank(n, 0); int base = 1; while (maxd > 0) { count.assign(10, 0); for (int i = 0; i < n; ++i) { count[(nums[i]/base)%10]++; } for (int i = 1; i < 10; ++i) { count[i] += count[i-1]; } for (int i = n-1; i >= 0; --i) { rank[--count[(nums[i]/base)%10]] = nums[i]; } for (int i = 0; i < n; ++i) { nums[i] = rank[i]; } maxd--; base *= 10; } return nums; } // 桶排序 (20 ms) vector<int> bucketSort(vector<int>& nums) { int n = nums.size(); int maxv = *max_element(nums.begin(), nums.end()); int minv = *min_element(nums.begin(), nums.end()); int bs = 1000; int m = (maxv-minv)/bs+1; vector<vector<int> > bucket(m); for (int i = 0; i < n; ++i) { bucket[(nums[i]-minv)/bs].push_back(nums[i]); } int idx = 0; for (int i = 0; i < m; ++i) { int sz = bucket[i].size(); bucket[i] = quickSort(bucket[i]); for (int j = 0; j < sz; ++j) { nums[idx++] = bucket[i][j]; } } return nums; } // 堆排序(32 ms) void adjust(vector<int>& nums, int p, int s) { while (2*p+1 < s) { int c1 = 2*p+1; int c2 = 2*p+2; int c = (c2<s && nums[c2]>nums[c1]) ? c2 : c1; if (nums[c] > nums[p]) swap(nums[c], nums[p]); else break; p = c; } } vector<int> heapSort(vector<int>& nums) { int n = nums.size(); for (int i = n/2-1; i >= 0; --i) { adjust(nums, i, n); } for (int i = n-1; i > 0; --i) { swap(nums[0], nums[i]); adjust(nums, 0, i); } return nums; } };