题目描述
Given an array of integers, return indices of the two numbers such that they add up to a specific target.
给定一个整数数组,返回两个数字的指数,使它们相加到特定目标。
You may assume that each input would have exactly one solution, and you may not use the same element twice.
您可以假设每个输入都具有完全一个解决方案,并且您可能不会使用* same *元素两次。
Example:
Given nums = [2, 7, 11, 15], target = 9,
Because nums[0] + nums[1] = 2 + 7 = 9,
return [0, 1].
思路与实现
使用 Map ,O(n) 时间复杂度
class Solution {
public int[] twoSum(int[] nums, int target) {
Map<Integer, Integer> map = new HashMap<>();
int[] res = new int[2];
for (int i = 0; i < nums.length; i++) {
map.put(nums[i], i);
}
for (int i = 0; i < nums.length; i++) {
int tem = target - nums[i];
if (map.containsKey(tem) && map.get(tem) != i) {
res[0] = i;
res[1] = map.get(tem);
break;
}
}
return res;
}
}
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