1.hashMap方法O(n)空间换时间
public class Solution { public int[] twoSum(int[] numbers, int target) { HashMap<Integer,Integer> hash=new HashMap<Integer,Integer>(); int ans[]=new int[2]; for(int i=0;i<numbers.length;i++) { if(hash.containsKey(target-numbers[i])) { ans[0]=hash.get(target-numbers[i])+1; ans[1]=i+1; return ans; } else hash.put(numbers[i],i); } return ans; } }
2. 排序后获取两个值
class node implements Comparable<node> { int x; int y; public int compareTo(node n) { return this.x-n.x; } public node(int x,int y) { this.x=x; this.y=y; } } public class Solution { public int[] twoSum(int[] numbers, int target) { node n[]=new node[numbers.length]; for(int j=0;j<numbers.length;j++) { n[j]=new node(numbers[j],j+1); } Arrays.sort(n); int ans[]=new int[2]; int low=0; int high=numbers.length-1; while(low<high) { int sum=n[low].x+n[high].x; if(sum==target) { ans[0]=n[low].y; ans[1]=n[high].y; if(n[low].y>n[high].y) { ans[0]=n[high].y; ans[1]=n[low].y; } break; } else if(sum>target) high--; else low++; } return ans; } }
原文：http://www.cnblogs.com/hansongjiang/p/3864087.html
