【算法】归并排序 merge sort

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#include <stdio.h>#include <stdlib.h>#include <string.h>int a[15] = {15,14,13,12,11,10, 9, 8, 7, 6, 5, 4, 3, 2, 1};void merge_sort (int l_num, int h_num){int k = l_num;int m = (h_num+l_num)/2+1;int i = 0;int *b = NULL;int j = 0;        printf("low index is %d, high index is %d.\n", l_num, h_num);if (l_num == h_num){printf("We have got to the leaf.\n");return;}merge_sort(l_num,(h_num+l_num)/2);merge_sort((h_num+l_num)/2+1, h_num);b = malloc((h_num-l_num+1)*sizeof(int));        if (NULL == b)        {                printf("Failed to alloc memory.\n");return;        }printf ("Low index is %d, high index is %d.\n", l_num, h_num);for (j = 0; j <= h_num-l_num; j++){if ((m > h_num)||(a[k] < a[m])){b[j]=a[k++];}else{b[j]=a[m++];}}for (j = l_num; j <= h_num; j++){a[j] = b[i++];printf("Index: %d, Num: %d.\n", j, a[j]);}free(b);}void main(){int i = 0;merge_sort(0, 14);for (i=0; i<14; i++){printf ("Final result index: %d, %d.\n", i, a[i]);}return;}

归并排序的算法复杂度为 n*lgn

插入排序的复杂度为 n*n,

当n增长到 30后，归并算法速度快

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