java 寻找两个数组的交集
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Finding the intersection of two arrays
提问by Alexandr Melnik
My aim is to find out values of intersection of arrays a and b and store them into a new array c so the printout will be : 3,10,4,8. How do I assign given values to a 3rd array c ?
我的目标是找出数组 a 和 b 的交集值并将它们存储到一个新数组 c 中，这样打印输出将是：3,10,4,8。如何将给定的值分配给第三个数组 c ？
public static void main(String[] args) {
int a[] = {3, 10, 4, 2, 8};
int[] b = {10, 4, 12, 3, 23, 1, 8};
int[] c;
int i=0;
for(int f=0;f<a.length;f++){
for(int k=0;k<b.length;k++){
if(a[f]==b[k]){
//here should be a line that stores equal values of 2 arrays(a,b) into array c
}
}
}
for (int x=0; x<c.length; x++){
System.out.println(c[i]);
}
}
}
回答by sakthisundar
This should be an easy way to do.
这应该是一个简单的方法。
int a[] = {3, 10, 4, 2, 8};
int[] b = {10, 4, 12, 3, 23, 1, 8};
List<Integer> aList = Arrays.asList(a);
List<Integer> bList = Arrays.asList(b);
aList.retainAll(bList);
System.out.println(" a intersection b "+aList);
int[] c = aList.toArray(new int[0]);
回答by taufique
public static void main(String[] args) {
int a[] = {3, 10, 4, 2, 8};
int[] b = {10, 4, 12, 3, 23, 1, 8};
int[] c = new int[(int)Math.min(a.length, b.length)];
int i=0;
for(int f=0;f<a.length;f++){
for(int k=0;k<b.length;k++){
if(a[f]==b[k]){
c[i] = a[f];
i++;
}
}
}
for (int x=0; x<i; x++){
System.out.println(c[x]);
}
}
}
Hope it helps. Or if you have time complexity issue then try Java Set.
希望能帮助到你。或者，如果您有时间复杂度问题，请尝试Java Set。
回答by Bhesh Gurung
You can take a help of temporary variable (but this is basically reinventing the wheel, if you are not required to do so) -
您可以借助临时变量（但这基本上是在重新发明轮子，如果您不需要这样做）-
int[] c = new int[0];
//...
if(a[f] == b[k]) {
int[] temp = c;
c = new int[c.length + 1];
for(int i=0; i<temp.length; i++) {
c[i] = temp[i];
}
c[c.length - 1] = a[f];
}
//...
回答by banjara
if permitted use ArrayList for c, its growable array
如果允许，将 ArrayList 用于 c，它的可增长数组
ArrayList c = new ArrayList();
.
.
.
.
.
c.add(a[f]);
also if permitted to sort arrays, i recommend you to sort smaller array and then iterate over larger array and binary search in smaller array.
此外，如果允许对数组进行排序，我建议您对较小的数组进行排序，然后迭代较大的数组并在较小的数组中进行二分搜索。
回答by Code-Apprentice
First you need to allocate space for your array:
首先，您需要为数组分配空间：
int[] c = new int[SOME_SIZE];
The hard part is figuring out how much SOME_SIZEshould be. Since you are calculating an intersection, the most it can be is the size of the smallest of aand b.
困难的部分是弄清楚SOME_SIZE应该是多少。因为你是计算一个路口，也可以是最深的是最小的尺寸a和b。
Finally, to assign an element in the array, you just do
最后，要在数组中分配一个元素，您只需执行
c[idx] = a[f]
Now you need to keep track of where idxgoes. I suggest starting with idx = 0and incrementing it each time you find a new element to add to c.
现在您需要跟踪idx去向。我建议idx = 0每次找到要添加到c.
