[LeetCode 1] Two Sum

import java.util.HashMap;
public class TwoSum {    
    public static void main(String[] args) {
        int[] input = { 2, 7, 11, 2 };
        int target = 4;
        int[] result = TwoSum2(input, target);
        for (int i = 0; i < result.length; i++) {
            System.out.println(result[i]);
        }

    }

    // 如果input数组是升序
    public static int[] TwoSum1(int[] input, int target) {
        int[] result = new int[2];
        int index1 = 0;
        int index2 = result.length;

        for (int i = 0; i < result.length; i++) {
            if (input[index1] + input[index2] == target) {
                result[0] = index1 + 1;
                result[1] = index2 + 1;

            } else if (input[index1] + input[index2] < target) {
                index1++;
            } else {
                index2--;
            }
        }

        return result;
    }

    // 如果input数组是无序,map中key保存需要的数值，value保存索引
    public static int[] TwoSum2(int[] input, int target) {
        int[] result = new int[2];
        HashMap<Integer, Integer> map = new HashMap<Integer, Integer>();

        for (int i = 0; i < input.length; i++) {
            if (map.containsKey(input[i])) {
                result[0] = map.get(input[i]) + 1;//map的value保存另一个索引
                result[1] = i + 1;//当前i记录当前的索引
            }
            else {
                map.put(target - input[i], i);
            }
        }

        return result;
    }

}