谁能向我解释实现mergeSort算法的这种非破坏性函数与该函数/ mergeSort算法的破坏性影响之间的区别?
public class MergeSort{
public static int[] merge(int[] A, int[] B){
System.out.println("merge: |A|="+A.length+", |B|="+B.length);
for(int i=0; i<A.length; i+=1) System.out.print(A[i] + ",");
System.out.println();
for(int i=0; i<B.length; i+=1) System.out.print(B[i] + ",");
System.out.println();
int [] C = new int[ A.length + B.length ];
int a = 0, b = 0;
for( int c = 0; c < C.length; c+=1 ){
if (a == A.length ){
C[c] = B[b];
b+=1;
}else if (b == B.length ){
C[c] = A[a];
a+=1;
}else{
if (A[a] < B[b]){
C[c] = A[a];
a+=1;
}else{
C[c] = B[b];
b+=1;
}
}
}
for(int i=0;i<C.length;i+=1) System.out.print(C[i] + ",");
System.out.println();
return C;
}
public static int[] mergeSort(int[] M){
System.out.println("mergesort : |M|="+M.length);
for(int i=0; i<M.length; i+=1) System.out.print(M[i] + ",");
System.out.println();
if (M.length ==1){
int [] C = new int[1];
C[0] = M[0];
return C;
}
int[] A = new int[ M.length/2 ];
System.arraycopy(M,0,A,0,M.length/2);
int[] AA = mergeSort(A);
int[] B = new int[ M.length - M.length/2 ];
System.arraycopy(M,M.length/2,B, 0, M.length - M.length/2);
int[] BB = mergeSort(B);
return merge(AA,BB);
}// mergeSort
}
如上所述,我知道此函数返回输入数组的“副本”(非解构)。如何将其更改为破坏性函数,换句话说,输入数组本身会发生突变,而不是产生副本。
最佳答案
您可以很容易地覆盖原始数组中的值,假设您的mergeSort()方法执行了预期的工作,则这样的工作就很好。
public void overwritingMergeSort(int[] M) {
int[] sorted = mergeSort(M);
for(int i = 0; i < sorted.length; i++) {
M[i] = sorted[i];
}
}
int[] arr = new int[]{2,5,1,4,3};
System.out.println(Arrays.toString(arr));
overwritingMergeSort(arr);
System.out.println(Arrays.toString(arr));
打印:
[2,5,1,4,3]
[1,2,3,4,5]