算法练习（4）：牛客在线编程05 哈希

package jz.bm;import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.HashSet;public class bm5 {/*** BM50 两数之和*/public int[] twoSum (int[] numbers, int target) {int[] res = new int[2];HashMap<Integer, Integer> map = new HashMap<>();for (int i = 0; i < numbers.length; i++) {if (map.containsKey(target - numbers[i])) {res[0] = map.get(target - numbers[i]) + 1;res[1] = i + 1;return res;} else {map.put(numbers[i], i);}}return res;}/*** BM51 数组中出现次数超过一半的数字*/public int MoreThanHalfNum_Solution(int [] array) {HashMap<Integer, Integer> map = new HashMap<>();for (int i = 0; i < array.length; i++) {if (map.containsKey(array[i])) {map.put(array[i], map.get(array[i]) + 1);} else {map.put(array[i], 1);}if (map.get(array[i]) > array.length / 2) {return array[i];}}return array[0];}/*** BM52 数组中只出现一次的两个数字*/public int[] FindNumsAppearOnce (int[] array) {int[] res = new int[2];HashMap<Integer, Integer> map = new HashMap<>();for (int k : array) {if (map.containsKey(k)) {map.put(k, 2);} else {map.put(k, 1);}}ArrayList<Integer> list = new ArrayList<>();for (int j : array) {if (map.get(j) == 1) {list.add(j);}}res[0] = Math.min(list.get(0), list.get(1));res[1] = Math.max(list.get(0), list.get(1));return res;}/*** BM53 缺失的第一个正整数*/public int minNumberDisappeared (int[] nums) {Arrays.sort(nums);HashMap<Integer, Integer> map = new HashMap<>();for (int i = 0; i < nums.length; i++) {map.put(nums[i], i);}for (int i = 1; i < Integer.MAX_VALUE; i++) {if (!map.containsKey(i)) {return i;}}return -1;}/*** BM54 三数之和*/public ArrayList<ArrayList<Integer>> threeSum(int[] num) {ArrayList<ArrayList<Integer>> lists = new ArrayList<>();Arrays.sort(num);HashMap<Integer, Integer> map = new HashMap<>();for (int i = 0; i < num.length; i++) {map.put(num[i], i);}int a, b, c;for (int i = 0; i < num.length; i = map.get(a) + 1) {a = num[i];for (int j = i + 1; j < num.length; j = map.get(b) + 1) {b = num[j];c = -a - b;if (map.containsKey(c) && map.get(c) > j) {ArrayList<Integer> list = new ArrayList<>();list.add(a);list.add(b);list.add(c);lists.add(list);}}}return lists;}
}