合并排序

合并排序

public class hebing {
public static void main(String args[]){

int[] data = new int[] { 5, 3, 6, 2, 1, 9, 4, 8, 7 };
mergeSort(data,0,8);
for (int i = 0; i < data.length; i++) {
System.out.print(data[i] + "\t");
}

}
public static void mergeSort(int a[],int left,int right){
if(left<right){
int middle=(left+right)/2;
mergeSort(a,left,middle);
mergeSort(a,middle+1,right);
merge(a,left,middle,right);
}
}
public static void merge(int[] data, int left, int center, int right) {
// 创建一个临时数组，将data数组分为两部分(两部分已经排好序)left- center-1，center - right(排好序的两部分)，进行汇总

//汇总 ,data[left]与data[center],小者放入临时数组第一位，然后将比较小的那部分后一位比较
int[] tmpArr = new int[data.length];
int mid = center + 1;
int third = left;
int tmp = left;
while (left <= center && mid <= right) {

if (data[left] <= data[mid]) {
tmpArr[third++] = data[left++];
} else {
tmpArr[third++] = data[mid++];
}
} 

//两部分中剩余的部分放进临时数组（实际只有一部分会有剩余）
while (mid <= right) {
tmpArr[third++] = data[mid++];
}
while (left <= center) {
tmpArr[third++] = data[left++];
}
// 将临时数组中的内容拷贝回原数组中
while (tmp <= right) {
data[tmp] = tmpArr[tmp++];
}
}

}