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package class_2022_04_2_week;
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import java.util.HashMap;
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// 来自百度
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// 给出一个长度为n的01串，现在请你找到两个区间，
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// 使得这两个区间中，1的个数相等，0的个数也相等
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// 这两个区间可以相交，但是不可以完全重叠，即两个区间的左右端点不可以完全一样
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// 现在请你找到两个最长的区间，满足以上要求。
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public class Code05_TowLongestSubarraySame01Number {
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public static int longest1(int[] arr) {
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HashMap<Integer, HashMap<Integer, Integer>> map = new HashMap<>();
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for (int i = 0; i < arr.length; i++) {
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int zero = 0;
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int one = 0;
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for (int j = i; j < arr.length; j++) {
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zero += arr[j] == 0 ? 1 : 0;
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one += arr[j] == 1 ? 1 : 0;
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map.putIfAbsent(zero, new HashMap<>());
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map.get(zero).put(one, map.get(zero).getOrDefault(one, 0) + 1);
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}
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}
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int ans = 0;
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for (int zeros : map.keySet()) {
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for (int ones : map.get(zeros).keySet()) {
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int num = map.get(zeros).get(ones);
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if (num > 1) {
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ans = Math.max(ans, zeros + ones);
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}
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}
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}
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return ans;
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}
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public static int longest2(int[] arr) {
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int leftZero = -1;
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int rightZero = -1;
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int leftOne = -1;
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int rightOne = -1;
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for (int i = 0; i < arr.length; i++) {
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if (arr[i] == 0) {
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leftZero = i;
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break;
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}
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}
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for (int i = 0; i < arr.length; i++) {
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if (arr[i] == 1) {
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leftOne = i;
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break;
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}
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}
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for (int i = arr.length - 1; i >= 0; i--) {
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if (arr[i] == 0) {
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rightZero = i;
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break;
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}
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}
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for (int i = arr.length - 1; i >= 0; i--) {
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if (arr[i] == 1) {
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rightOne = i;
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break;
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}
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}
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int p1 = rightZero - leftZero;
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int p2 = rightOne - leftOne;
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return Math.max(p1, p2);
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}
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public static int[] randomArray(int len) {
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int[] ans = new int[len];
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for (int i = 0; i < len; i++) {
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ans[i] = (int) (Math.random() * 2);
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}
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return ans;
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}
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public static void main(String[] args) {
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int n = 500;
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int testTime = 200;
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System.out.println("测试开始");
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for (int i = 0; i < testTime; i++) {
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int size = (int) (Math.random() * n) + 2;
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int[] arr = randomArray(size);
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int ans1 = longest1(arr);
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int ans2 = longest2(arr);
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if (ans1 != ans2) {
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System.out.println("出错了!");
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break;
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}
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}
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System.out.println("测试结束");
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}
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}
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