import java.util.HashMap;
public class TwoSum {
/**
* one pass
* 要注意map.put要放在for末尾，对于case[3, 3], target=6的情况，如果放在开头会覆盖第一个3
*/
public int[] twoSum2(int[] nums, int target) {
HashMap map = new HashMap<>();
for (int i = 0; i < nums.length; i++) {
if (map.containsKey(target - nums[i])) {
return new int[] {map.get(target - nums[i]), i};
}
map.put(nums[i], i);
}
return null;
}
}