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Copy pathTwoSum.java
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35 lines (28 loc) · 924 Bytes
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/*
1. Two Sum
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.
Example:
Given nums = [2, 7, 11, 15], target = 9,
Because nums[0] + nums[1] = 2 + 7 = 9,
return [0, 1].
*/
package twopointers;
import java.util.HashMap;
public class TwoSum {
public static int[] twoSum(int[] nums, int target) {
if (nums == null || nums.length < 2) {
return null;
}
HashMap<Integer, Integer> map = new HashMap<>();
for (int i = 0; i < nums.length; i++) {
if (map.containsKey(nums[i])) {
return new int[]{map.get(nums[i]), i};
} else {
map.put(target - nums[i], i);
}
}
return null;
}
//第二种解法，先排序然后双指针
}