37 lines
1.1 KiB
Java
37 lines
1.1 KiB
Java
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import java.util.ArrayList;
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import java.util.Arrays;
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import java.util.List;
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public class ReverseElements {
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// 双指针 ArrayList 反转元素 出自 java.util.Collections#reverse
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public static void array() {
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List<Integer> list = new ArrayList<>(Arrays.asList(1, 2, 3, 4, 5, 6, 7));
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int size = list.size();
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Integer x, y;
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for (int begin = 0, mid = size >> 1, end = size - 1; begin < mid; begin++, end--) {
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x = list.get(begin);
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y = list.get(end);
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list.set(begin, y);
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list.set(end, x);
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}
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System.out.println(list);
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}
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// 双指针反转字符串 String无法直接操作内部的char数组 避免不了2倍内存开销
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public static void main(String[] args) {
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String str = "1234567";
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char[] chars = str.toCharArray();
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int len = chars.length;
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char x, y;
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for (int index = 0, mid = len >> 1, end = len - 1; index < mid; index++, end--) {
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x = chars[index];
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y = chars[end];
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chars[index] = y;
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chars[end] = x;
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}
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System.out.println(new String(chars));
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}
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}
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