LeetCode- Two Sum

public class Solution {
    public int[] TwoSum(int[] nums, int target) 
    {
        var hash = new Dictionary<int, int>();
    	for(var i = 0;i < nums.Length; i++){
    		if(!hash.ContainsKey(nums[i])){
    			hash.Add(nums[i], i);
    		}
    		else{
    			if(target == nums[i] * 2){
    				return new int[2]{hash[nums[i]] + 1, i + 1};
    			}
    			// if one number appears twice and not equals to target half , just take the first one
    		}
    	}
    	
    	foreach(var k in hash.Keys){
    		var k2 = target - k;
    		if(hash.ContainsKey(k2) && hash[k2] != hash[k]){
    			var index1 = hash[k];
    			var index2 = hash[k2];
    			
    			if(index1 > index2){
    				return new int[2]{index2 + 1, index1 + 1};
    			}else{
    				return new int[2]{index1 + 1, index2 + 1};
    			}
    		}
    	}
    	
    	return null;
    }
}

LeetCode- Two Sum

原文：http://blog.csdn.net/lan_liang/article/details/50144879