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| 归并排序：
public class MergeSort {
public static void main(String[] args) {
int[] a = {8, 45, 43, 67, 23, 5, 3, 88, 55};
System.out.println("排序前" + Arrays.toString(a));
int[] ret = sort(a, 0, a.length-1);
System.out.println("排序后" + Arrays.toString(ret));
}
public static int[] sort(int[] a, int low, int high) {
int mid = (low + high)/2;
if (low < high) {
sort(a, low, mid);
sort(a, mid+1, high);
merge(a, low, mid, high);
}
return a;
}
public static void merge(int[] a, int low, int mid, int high) {
int[] temp = new int[high-low+1];
int i = low;
int j = mid+1;
int k = 0;
// 把较小的数先移到新数组中
while (i<=mid && j<=high) {
if (a[i] < a[j]) {
temp[k++] = a[i++];
} else {
temp[k++] = a[j++];
}
}
// 把左边剩余的数移入数组
while (i<=mid) {
temp[k++] = a[i++];
}
// 把右边边剩余的数移入数组
while (j<=high) {
temp[k++] = a[j++];
}
// 把新数组中的数覆盖原数组
for (int x = 0; x < temp.length; x++) {
a[x+low] = temp[x];
}
}
}
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