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package class007;
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import java.util.HashMap;
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import java.util.Map.Entry;
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public class Code03_FindHalfMajority {
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public static int halfMajor(int[] arr) {
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int cand = 0;
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int HP = 0;
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// 遍历一遍数组arr，一次删掉两个不同的数，谁会剩下来，谁就是cand
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for (int i = 0; i != arr.length; i++) {
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if (HP == 0) { // 如果没有候选
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cand = arr[i];
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HP = 1;
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} else if (arr[i] == cand) {
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HP++;
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} else {
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HP--;
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}
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}
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if (HP == 0) {
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return -1;
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}
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HP = 0;
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for (int i = 0; i != arr.length; i++) {
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if (arr[i] == cand) {
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HP++;
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}
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}
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return HP > arr.length / 2 ? cand : -1;
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}
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// for test
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public static int right(int[] arr) {
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HashMap<Integer, Integer> map = new HashMap<>();
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for (int cur : arr) {
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if (!map.containsKey(cur)) {
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map.put(cur, 0);
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}
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map.put(cur, map.get(cur) + 1);
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}
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for (Entry<Integer, Integer> entry : map.entrySet()) {
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if (entry.getValue() > arr.length / 2) {
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return entry.getKey();
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}
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}
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return -1;
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}
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// for test
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public static int[] genareteRandomArray(int len, int max) {
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int[] ans = new int[(int) (Math.random() * len) + 1];
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for (int i = 0; i < ans.length; i++) {
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ans[i] = (int) (Math.random() * max) + 1;
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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 len = 100;
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int max = 10;
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int testTime = 100000;
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System.out.println("test begin");
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for (int i = 0; i < testTime; i++) {
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int[] arr = genareteRandomArray(len, max);
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int ans1 = halfMajor(arr);
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int ans2 = right(arr);
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if (ans1 != ans2) {
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System.out.println("Oops!");
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break;
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}
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}
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System.out.println("test end");
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}
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}
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