【LeetCode】1.Two Sum解题报告

【LeetCode】1.Two Sum解题报告

tags: Array HashTable

题目地址：https://leetcode.com/problems/two-sum/#/description

题目描述：

  Given an array of integers, return indices of the two numbers such that they add up to a specific target.

  You may assume that each input would have exactly one solution, and you may not use the same element twice.

Examples:

  Given nums = [2, 7, 11, 15], target = 9,

  Because nums[0] + nums[1] = 2 + 7 = 9,

  return [0, 1].

Solutions:

public class Solution {
public int[] twoSum(int[] nums, int target) {
int[] result = new int[2];
Map<Integer, Integer> map = new HashMap<Integer,Integer>();
for (int i = 0; i < nums.length; i++) {
if (map.containsKey(target - nums[i])) {
result[1] = i ;
result[0] = map.get(target - nums[i]);
return result;
}
map.put(nums[i], i);
}
return result;
}
}

  思想就是说从数组nums第一个数开始，从前往后看是否map中存在值为target-nums[i]的数，不存在则将有前到后所有值写入map，直到找到和为target的两个数中的后一个数为止。

Date：2017年5月24日