leetcode 1. Two Sum -----java
題目:
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.
Example:
Given nums = [2, 7, 11, 15], target = 9, Because nums[0] + nums[1] = 2 + 7 = 9, return [0, 1].
解析:利用hashmap,key存放數值,value存放出現的位置。從前到後進行遍歷,將target值減去當前的值,看是否存在map中,
若存在map中則取出相應的標號,退出。
java程式碼實現:
public class Solution {
public int[] twoSum(int[] nums, int target) {
HashMap<Integer, Integer> map = new HashMap<Integer, Integer>();
int result[] = new int[2];
for (int i = 0; i < nums.length; i++){
int num = target - nums[i];
if(map.containsKey(num)){
result[0] = map.get(num);
result[1] = i;
return result;
}
map.put(nums[i], i);
}
return result;
}
}