日期:2014-05-20 浏览次数:20775 次
public static int[] max5(List<Integer> lst)
{
int count = Math.min(5, lst.size());
int[] b = new int[count]; //当然也可以用list来做,但是用数组效率要好一些
for (int i=0; i<count; i++) b[i] = lst.get(i); //相当于递归做法的获得b,
//当然递归做法是获得lst的后5个元素,这里是前5个元素,获得后5个元素用lst.size()-count+i就可以了
for (int i=count; i<lst.size(); i++) {
int a = lst.get(i); //这里相当于1L的递归做法的 a = lst.remove(0);
for (int j=0; j<count; j++) {
if (a > result[j]) { //相当于交换a和b的某个位置的数据
int t = result[j];
b[j] = a; //这里就相当于1L的lst.set(i, a)
a = t;
}
}
}
return b;
}
------解决方案--------------------
1L是对的
用数组的话会更快点
import java.util.Arrays;
public class MyTop {
static final int[] NUMS = new int[]{12,127,85,66,27,34,15,344,156,344,29,47};
static final int SIZE = 5;//前5个最大数
static int[] TOPS = new int[SIZE];//存放最大值的数组
public static void main(String[] args) {
long start = System.nanoTime();//开始
find(NUMS.length, SIZE);//获取最大数
System.out.println(Arrays.toString(TOPS));//打印
long end = System.nanoTime();//结束
System.out.println("time = " + (end - start) / 1e9 + " seconds");//输出时间
}
static void find(int total,int size){
//前5个数直接存入数组
for(int i = 0;i < size;++i){
TOPS[i] = NUMS[i];
}
setMin();
for(int i = size;i < total;++i){
//如果当前数比arr[0]大,将arr[0]替换为num,再获取最小值放入arr[0]
if(NUMS[i] > TOPS[0]){
TOPS[0] = NUMS[i];
setMin();
}
}
}
static void setMin(){
int min = TOPS[0];
int index = 0;
for(int i = 1;i < TOPS.length;i++){
if(TOPS[i] < min){
min = TOPS[i];
index = i;
}
}
int temp = TOPS[0];
TOPS[0] = TOPS[index];
TOPS[index] = temp;
}
}
------解决方案--------------------
/**
* 取得数组中最大的子数组</br>
* 在长数组中取得前N个值,作为最大的子数组,如果遇到后面的数比子数组中最小值小,则将此值设入子数组中
*/
public class MaxSubArray {
private int[] ints = null;
private int count = 1;
public MaxSubArray(int[] ints) {
this.ints = ints;
}
public MaxSubArray(int[] ints, int count) {
this.ints = ints;
this.count = count;
}
public int[] getMaxArray() {
int[] mis = new int[count];
System.arraycopy(ints, 0, mis, 0, count);
Info info = min(mis);
for (int i = count; i < ints.length; i++) {
if (ints[i] > info.min) {
mis[info.point] = ints[i];
info = min(mis);
}
}
Arrays.sort(mis);
return mis;
}
private Info min(final int[] ints) {
Info info = new Info();
info.min = ints[0];
info.point = 0;
for (int i = 1; i < ints.length; i++) {
if (info.min > ints[i]) {
info.min = ints[i];
info.point = i;
}
}
return info;
}
private class Info {
private int min;
private int point;
}
}