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package class_2022_09_2_week;
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// 来自学员问题
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// 本文件仅为贪心的验证文件
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// 有一个数组包含0、1、2三种值，
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// 有n次修改机会，第一种将所有连通的1变为0，修改次数-1
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// 第二种将所有连通的2变为1或0，修改次数-2，
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// 返回n次修改机会的情况下连通的0最长能是多少？
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// 1 <= arr长度 <=10^6
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// 0 <= 修改机会 <=10^6
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public class Code04_RunThroughZero1 {
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public static int best1(int[] arr) {
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int zero = 0;
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int two = 0;
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int n = arr.length;
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for (int num : arr) {
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zero += num == 0 ? 1 : 0;
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two += num == 2 ? 1 : 0;
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}
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if (zero == n) {
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return 0;
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}
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if (two == n) {
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return 2;
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}
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int ans = Integer.MAX_VALUE;
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for (int i = 0; i < n; i++) {
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if (arr[i] != 0 && (i == 0 || arr[i - 1] != arr[i])) {
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if (arr[i] == 2) {
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ans = Math.min(ans, 2 + Math.min(best1(change(arr, i, 1)), best1(change(arr, i, 0))));
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} else {
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ans = Math.min(ans, 1 + best1(change(arr, i, 0)));
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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[] change(int[] arr, int i, int to) {
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int l = i;
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int r = i;
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while (l >= 0 && arr[l] == arr[i]) {
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l--;
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}
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while (r < arr.length && arr[r] == arr[i]) {
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r++;
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}
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int[] ans = new int[arr.length];
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for (i = 0; i < arr.length; i++) {
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ans[i] = arr[i];
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}
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for (i = l + 1; i < r; i++) {
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ans[i] = to;
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}
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return ans;
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}
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public static int cost(int[] arr, int l, int r) {
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int num0 = 0;
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int num2 = 0;
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int n = r - l + 1;
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for (int i = l; i <= r; i++) {
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num0 += arr[i] == 0 ? 1 : 0;
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num2 += arr[i] == 2 ? 1 : 0;
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}
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if (num0 == n) {
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return 0;
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}
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if (num2 == n) {
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return 2;
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}
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int area2 = arr[l] == 2 ? 1 : 0;
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for (int i = l; i < r; i++) {
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if (arr[i] != 2 && arr[i + 1] == 2) {
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area2++;
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}
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}
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boolean has1 = false;
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int areaHas1No0 = 0;
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for (int i = l; i <= r; i++) {
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if (arr[i] == 0) {
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if (has1) {
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areaHas1No0++;
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}
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has1 = false;
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}
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if (arr[i] == 1) {
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has1 = true;
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}
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}
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if (has1) {
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areaHas1No0++;
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}
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return 2 * area2 + areaHas1No0;
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}
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public static int[] randomArray(int n) {
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int[] ans = new int[n];
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for (int i = 0; i < n; i++) {
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ans[i] = (int) (Math.random() * 3);
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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 = 9;
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int testTimes = 1000;
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System.out.println("测试开始");
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for (int i = 0; i < testTimes; i++) {
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int[] arr = randomArray(n);
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int ans1 = best1(arr);
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int ans2 = cost(arr, 0, arr.length - 1);
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if (ans1 != ans2) {
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for (int num : arr) {
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System.out.print(num + " ");
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}
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System.out.println();
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System.out.println(ans1);
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System.out.println(ans2);
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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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