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package com.sample.suncht.algo;
import java.util.HashMap;
import java.util.Map;
/**
* 1. 两数之和
* 给定一个整数数组 nums 和一个目标值 target,请你在该数组中找出和为目标值的那 两个 整数,并返回他们的数组下标。
* 示例:
* 给定 nums = [2, 7, 11, 15], target = 9
* 因为 nums[0] + nums[1] = 2 + 7 = 9
* 所以返回 [0, 1]
*
* 时间复杂度:O(n), 空间复杂度:O(n)
*
* @author sunchangtan
* @date 2019/3/1 12:49
*/
public class TwoSum {
public int[] twoSum(int[] nums, int target) {
int[] result = new int[2];
Map<Integer, Integer> map = new HashMap<>();
for (int i = 0, len = nums.length; i < len; i++) {
int tmp = target - nums[i];
if(map.containsKey(tmp)) {
result[0] = map.get(tmp);
result[1] = i;
break;
} else {
map.put(nums[i], i);
}
}
return result;
}
public static void main(String[] args) {
// int[] nums = new int[]{2, 7, 11, 15};
// int target = 9;
int[] nums = new int[]{2, 7, 11, 15, 9, 20};
int target = 35;
int[] result = new TwoSum().twoSum(nums, target);
System.out.println(result[0] + ", " + result[1]);
}
}