歸併排序

歸併排序是將兩個有序的子序列合併成一個有序序列的過程，採用分治法。

java實現：

public class MergeSort {

public int[] mergerSort(int[] arrays){
int[] tmp = new int[arrays.length];
mergSort(arrays,0,arrays.length -1,tmp);
return arrays;
}

public void mergSort(int[] arrays, int begin,int end,int[] tmp){
if(begin < end){
int mid = (begin + end)/2;
mergSort(arrays,begin,mid,tmp);
mergSort(arrays,mid+1,end,tmp);
merge(arrays,begin,mid,end,tmp);
}
}

public void merge(int[] arrays,int begin,int mid,int end,int[] tmp) {
int i = begin, j = mid+1;
int k = begin;
while(i <= mid && j <= end){
if(arrays[i] < arrays[j]){
tmp[k++] = arrays[i++];
} else {
tmp[k++] = arrays[j++];
}
}
if(i <= mid){
while(i<=mid){
tmp[k++] = arrays[i++];
}
}
if(j <= end){
while(j <= end){
tmp[k++] = arrays[j++];
}
}
for(int index = begin; index <= end; index++){
arrays[index] = tmp[index];
}
}

public static void main(String[] args){
int[] arrays = {10,5,4,8,74,58,12,14,14,56,3,1,11,57,41,102,13,-9,0};
arrays = new MergeSort().mergerSort(arrays);
for(int i = 0; i < arrays.length; i++){
System.out.print(arrays[i]);
System.out.print(",");
}
}

}