归并排序递归方式和非递归（Java）

归并排序递归方式

public class Test11 {
    // 归并排序
    // 非递归
    // 递归版本
    public static void main(String[] args) {
        int[] arr = new int[]{3,2,1,-1,231,31,31254};
        mergeSort02(arr);
        System.out.println(printArr(arr));
    }
    public static String printArr(int[] arr) {
        StringBuilder stringBuilder = new StringBuilder();
        for (int i = 0; i < arr.length; i++) {
            stringBuilder.append(arr[i]);
            stringBuilder.append(',');
        }
        return stringBuilder.toString();
    }

    public static void mergeSort1(int[] data){
        msort(data,0,data.length-1);
    }

    public static void msort(int[] data, int start, int end){
        if(start < end){
            int mid = (start + end) >>> 1;
            msort(data,start,mid);
            msort(data,mid+1,end); //当mid+1 == end时，子序列长度为1，退出msort，进入merge()排序
            merge(data,start,mid,end);
        }
    }

    public static void merge(int[] data, int start, int mid, int end){
        int s1 = start;     //子序列1在data[]的起始下标
        int s2 = mid + 1;  //子序列2在data[]的起始下标
        int[] tmp = new int[end - start +1];
        int index = 0; //临时数组tmp的下标
        while((s1 <= mid) && (s2 <= end)){ //两个序列都还没有完全放入tmp[]中
            if(data[s1] < data[s2]) tmp[index++] = data[s1++];
            else tmp[index++] = data[s2++];
        }
        while(s1 <= mid){ //第2个序列已经完全放入tmp中，由于s1本身是有序的，将s1剩下的元素直接放入
            tmp[index++] = data[s1++];
        }
        while(s2 <= end){
            tmp[index++] = data[s2++];
        }
        for(int i = 0; i < tmp.length; i++){
            data[start++] = tmp[i];
        }
    }

    // 非递归实现
    public static void mergeSort02(int[] data) {
        int k = 1;
        while(k < data.length) {
            merge(data, k);
            k *= 2;
        }
    }
    public static void merge(int[] data, int len) {
        int s1 = 0;
        int e1 = s1 + len-1;
        int s2 = e1 + 1;
        int e2 = s2 + len-1<data.length ? s2+len-1:data.length-1;
        int[] tmp = new int[data.length];
        int index = 0;
        while(s2 < data.length) {
            while((s1 <= e1) && (s2 <= e2)) {
                if (data[s1] < data[s2]) tmp[index++] = data[s1++];
                else tmp[index++] = data[s2++];
            }
            while(s1<=e1) {
                tmp[index++] = data[s1++];
            }
            while(s2 <= e2) {
                tmp[index++] = data[s2++];
            }
            s1 = e2 + 1;
            e1 = s1 + len -1;
            s2 = e1 + 1;
            e2 = s2+ len - 1 < data.length? s2+len -1: data.length-1;
        }
        while (s1 < data.length) {
            tmp[index++] = data[s1++];
        }
        for (int i = 0; i < data.length; i++) {
            data[i] = tmp[i];
        }
    }
}