zoukankan      html  css  js  c++  java
  • [Algorithms] Radix Sort

    Radix sort is another linear time sorting algorithm. It sorts (using another sorting subroutine) the numbers from their least significant digits to most significant digits. To guarantee the correctness of radix sort, the sorting subroutine must be stable. Moreover, each digit falls in a fixed range. For example, if the numbers are decimal, then all digits fall in [0, 9]. So counting sort is usually used as the subroutine.

    The code is as follows. For more on radix sort, please refer to Introduction to Algorithms, 3rd edition.

     1 #include <iostream>
     2 #include <vector>
     3 #include <ctime>
     4 #include <algorithm>
     5 
     6 using namespace std;
     7 
     8 int maximum(vector<int>& nums) {
     9     int mx = nums[0];
    10     for (int i = 1; i < (int)nums.size(); i++)
    11         mx = max(mx, nums[i]);
    12     return mx;
    13 }
    14 
    15 void countingSort(vector<int>& nums, int sig) {
    16     vector<int> counts(10, 0);
    17     for (int i = 0; i < (int)nums.size(); i++)
    18         counts[nums[i] / sig % 10]++;
    19     for (int i = 1; i < 10; i++)
    20         counts[i] += counts[i - 1];
    21     vector<int> sorted(nums.size());
    22     for (int i = nums.size() - 1; i >= 0; i--) {
    23         sorted[counts[nums[i] / sig % 10] - 1] = nums[i];
    24         counts[nums[i] / sig % 10]--;
    25     }
    26     swap(nums, sorted);
    27 }
    28 
    29 void radixSort(vector<int>& nums) {
    30     int mx = maximum(nums);
    31     for (int sig = 1; mx / sig; sig *= 10)
    32         countingSort(nums, sig);
    33 }
    34 
    35 void radixSortTest(void) {
    36     int len = 1000;
    37     vector<int> nums(len);
    38     srand((unsigned)time(NULL));
    39     for (int i = 0; i < (int)nums.size(); i++)
    40         nums[i] = rand() % (len + 1);
    41     vector<int> copy = nums;
    42     radixSort(nums);
    43     sort(copy.begin(), copy.end());
    44     for (int i = 0; i < (int)nums.size(); i++) {
    45         if (nums[i] != copy[i]) {
    46             printf("radixSort() test failed!
    ");
    47             return;
    48         }
    49     }
    50     printf("radixSort() test passed!
    ");
    51 }
    52 
    53 int main(void) {
    54     radixSortTest();
    55     system("pause");
    56     return 0;
    57 }
  • 相关阅读:
    Mysql 免密码登录,修改密码及忘记密码操作
    CentOS 6.9 升级MySQL 5.6.36到5.7.18
    【转载】详解布隆过滤器的原理、使用场景和注意事项
    AssemblyVersion、AssemblyFileVersion、AssemblyInformationalVersion 区别
    为什么要有财务自由【转】
    CacheManager.Core
    雪花算法,生成分布式唯一ID
    监控
    什么是并行、并发, 两者的区别是什么
    Emit用法
  • 原文地址:https://www.cnblogs.com/jcliBlogger/p/4564530.html
Copyright © 2011-2022 走看看