C ++中的3路合并排序
合并排序包括将数组递归分为两部分，进行排序，最后合并它们。合并排序的一种变体被视为3向合并排序，其中不是将数组分为2部分，而是将其分为3部分。
合并排序以递归方式将数组分解为大小为一半的子数组。同样，三向合并排序会将数组分解为大小为三分之一的子数组。
例子
Input : 46, -1, -44, 79, 31, -41, 11, 20 , 74, 94 Output : -44 -41 -1 11 20 31 46 74 79 94 Input : 24, -18 Output : -18 24
3路合并排序的时间复杂度为nlog3n。
示例
// C++ Program for performing 3 way Merge Sort
#include <bits/stdc++.h>
usingnamespacestd;
voidmerge1(intgArray1[], intlow1, intmid1,
intmid2, inthigh1, intdestArray1[]){
inti = low1, j = mid1, k = mid2, l = low1;
//在三个范围中选择较小的
while((i < mid1) && (j < mid2) && (k < high1)){
if(gArray1[i] < gArray1[j]){
if(gArray1[i] < gArray1[k]){
destArray1[l++] = gArray1[i++];
}
else{
destArray1[l++] = gArray1[k++];
}
}
else{
if(gArray1[j] < gArray1[k]){
destArray1[l++] = gArray1[j++];
}
else{
destArray1[l++] = gArray1[k++];
}
}
}
while((i < mid1) && (j < mid2)){
if(gArray1[i] < gArray1[j]){
destArray1[l++] = gArray1[i++];
}
else{
destArray1[l++] = gArray1[j++];
}
}
while((j < mid2) && (k < high1)){
if(gArray1[j] < gArray1[k]){
destArray1[l++] = gArray1[j++];
}
else{
destArray1[l++] = gArray1[k++];
}
}
while((i < mid1) && (k < high1)){
if(gArray1[i] < gArray1[k]){
destArray1[l++] = gArray1[i++];
}
else{
destArray1[l++] = gArray1[k++];
}
}
while(i < mid1)
destArray1[l++] = gArray1[i++];
while(j < mid2)
destArray1[l++] = gArray1[j++];
while(k < high)
destArray1[l++] = gArray1[k++];
}
voidmergeSort3WayRec(intgArray1[], intlow1,
inthigh1, intdestArray1[]){
if(high1 - low1 < 2)
return;
intmid1 = low1 + ((high1 - low1) / 3);
intmid2 = low1 + 2 * ((high1 - low1) / 3) + 1;
mergeSort3WayRec(destArray1, low1, mid1, gArray1);
mergeSort3WayRec(destArray1, mid1, mid2, gArray1);
mergeSort3WayRec(destArray1, mid2, high1, gArray1);
merge(destArray1, low1, mid1, mid2, high1, gArray1);
}
voidmergeSort3Way(intgArray1[], intn1){
if(n1 == 0)
return;
intfArray1[n];
for(inti = 0; i < n1; i++)
fArray1[i] = gArray1[i];
//排序功能
mergeSort3WayRec(fArray1, 0, n, gArray1);
for(inti = 0; i < n1; i++)
gArray1[i] = fArray1[i];
}
//驱动程式码
intmain(){
intdata1[] = {46, -1, -44, 79, 31,
-41, 11, 20, 74, 94};
mergeSort3Way(data1,10);
cout<< "After 3 way merge sort: ";
for(inti = 0; i < 10; i++){
cout<< data1[i] << " ";
}
return0;
}输出结果
After 3 way merge sort: -44 -41 -1 11 20 31 46 74 79 94