Given nums = [2, 7, 11, 15], target = 9,Because nums[0] + nums[1] = 2 + 7 = 9,return [0, 1].

package com.lifeibigdata.algorithms.leetcode;/** * Created by lifei on 16/5/27. * * 1 */public class TwoSum {    public static void main(String[] args) {        int[] nums = {0,3,7,9,11,14,16,17};        TwoSum ts = new TwoSum();//        int []res = ts.twoSum(nums,20);//        for (int i :res) {//            System.out.printf(i + " ");//        }        twoSum2(nums,20);    }    public int[] twoSum(int[] nums, int target) {        int[] res = new int[2];        for (int i = 0; i < nums.length; i++){            boolean flag = true;            for (int j = 0;j < nums.length; j++){                if (i == j) continue;                if (nums[i] + nums[j] == target){                    res[0] = i;                    res[1] = j;                    flag = false;                    break;                }            }            if (!flag) break;        }        return res;    }    static void twoSum2(int[] a,int sum){        int i = 0;        int j = a.length - 1;        while (i < j){            if (a[i] + a[j] < sum){                i++;            } else if (a[i] + a[j] > sum){                j--;            } else {                System.out.println(a[i]+"---"+a[j]);                i++;                j--;            }        }    }}