排序算法

冒泡排序，稳定，复杂度n*n

选择排序，不稳定，复杂度n*n

不稳定：

快速排序，递归实现，不稳定，复杂度n*log(n)，空间复杂度

堆排序，大小顶堆实现，不稳定，复杂度n*log(n)

稳定：

在快速排序中添加另外一个控制变量

合并排序，两个有序队列合并

1、快速排序示例

//快速排序示例#include <cstdio>#include <cstdlib>int p[50];int len;void input(){len = 20;int i;for(i = 0; i < len; ++ i)p[i] = rand() / 100;p[0] = p[1] = p[2] = 50;}void print(){int i;for(i = 0; i < len; ++ i)printf("%d ", p[i]);printf("\n");}void fsort(int l, int r)//快速排序{if(l >= r) return;int temp = p[l];int pl, pr;for(pl = l, pr = r;pl < pr;){for(;pl < pr;){if(p[pr] >= temp)pr --;elsebreak;}if(pl < pr) p[pl ++] = p[pr];for(;pl < pr;){if(p[pl] <= temp)pl ++;elsebreak;}if(pl < pr) p[pr --] = p[pl];}p[pr] = temp;fsort(l, pr - 1);fsort(pr + 1, r);}int main(){input();print();fsort(0, len - 1);print();return 0;}

2、堆排序示例

//堆排序示例#include <cstdio>#include <cstdlib>int p[50];int len;void input(){len = 25;int i;for(i = 1; i <= len; ++ i)p[i] = rand() / 100;p[1] = p[2] = 50;}void print(){int i;for(i = 1; i <= len; ++ i)printf("%d ", p[i]);printf("\n");}void swap(int x, int y){int temp = p[x];p[x] = p[y];p[y] = temp;}void fsort()//堆排序{int i;int q;for(i = len / 2; i >= 1; -- i)//小顶堆初始化{q = i;while(2 * q <= len){if(2 * q + 1 > len){if(p[q] > p[2 * q]){swap(q, 2 * q);q = 2 * q;}break;}else{if(p[2 * q] <= p[2 * q + 1]){if(p[q] > p[2 * q]){swap(q, 2 * q);q = 2 * q;}elsebreak;}else{if(p[q] > p[2 * q + 1]){swap(q, 2 * q + 1);q = 2 * q + 1;}elsebreak;}}}}int n = 1;while(n < len)//每次第一个数与最后一位数交换，这样循环len - 1遍，数组从大到小排序{swap(len - n + 1, 1);q = 1;while(2 * q < len - n + 1){if(2 * q + 1 >= len - n + 1){if(p[q] > p[2 * q]){swap(q, 2 * q);q = 2 * q;}elsebreak;}else{if(p[2 * q] <= p[2 * q + 1]){if(p[q] > p[2 * q]){swap(q, 2 * q);q = 2 * q;}elsebreak;}else{if(p[q] > p[2 * q + 1]){swap(q, 2 * q + 1);q = 2 * q + 1;}elsebreak;}}}n ++;}}int main(){input();print();fsort();print();return 0;}

3、归并排序

//归并排序示例#include <cstdio>#include <cstdlib>#include <cstring>int p[50];int _p[50];int len;void input(){len = 20;int i;for(i = 0; i < len; ++ i)_p[i] = p[i] = rand() / 100;_p[0] = p[0] = 50;_p[1] = p[1] = 50;_p[2] = p[2] = 50;}void print(){int i;for(i = 0; i < len; ++ i)printf("%d ", p[i]);printf("\n");}void fsort(int l, int r)//归并排序{if(l == r)return;int mid = (l + r) / 2;fsort(l, mid);fsort(mid + 1, r);int i, j, z;for(i = l, j = mid + 1, z = 0; i <= mid || j <= r;)//对两个有序数组进行排序{if(i > mid)_p[l + (z ++)] = p[j ++];else if(j > r)_p[l + (z ++)] = p[i ++];else{if(p[i] <= p[j])_p[l + (z ++)] = p[i ++];else_p[l + (z ++)] = p[j ++];}}//memcpy(p, _p, sizeof(_p));for(i = l; i <= r; ++ i)p[i] = _p[i];}int main(){input();print();fsort(0, len - 1);print();return 0;}