// @Title: 两数之和 (Two Sum)
// @Author: qisiii
// @Date: 2021-07-05 14:13:15
// @Runtime: 97 ms
// @Memory: 38.8 MB
// @comment: 
// @flag: 
class Solution {
    public int[] twoSum(int[] nums, int target) {
        int[] result=new int[2];
        if(nums.length<0){return result;}
      for(int i=0;i<nums.length;i++){
         
         
          int cha=target-nums[i];
          result[0]=i;
          for(int j=0;j<nums.length;j++){
              if(i==j){continue;}
              if(cha==nums[j]){
                 result[1]=j;
                  return result;
              }
          }
      }
      return result;
    }
}

// @Title: 两数之和 (Two Sum)
// @Author: qisiii
// @Date: 2021-12-16 13:27:45
// @Runtime: 4 ms
// @Memory: 39.7 MB
// @comment: 哈希
// @flag: BLUE
class Solution {
    public int[] twoSum(int[] nums, int target) {
        int[] result= new int[2];
        HashSet set=new HashSet();
        for (int num : nums) {
            set.add(num);
        }
        for(int i=0;i<nums.length;i++){
            int cha=target-nums[i];
            if (set.contains(cha)){
                for (int j = i+1; j < nums.length; j++) {
                    if (cha==nums[j]){
                        result[0]=i;
                        result[1]=j;
                    }
                }
            }
        }
        return result;

    }
}

// @Title: 两数之和 (Two Sum)
// @Author: qisiii
// @Date: 2024-04-10 21:30:50
// @Runtime: 55 ms
// @Memory: 43.6 MB
// @comment: 2024年重新开始计算-两数之和暴力循环
// @flag: RED
class Solution {
    public int[] twoSum(int[] nums, int target) {
        for(int i=0;i<nums.length;i++){
            for(int j=i+1;j<nums.length;j++){
                if(nums[i]+nums[j]==target){
                    return new int[]{i,j};
                }
            }
        }
        return null;
    }
}

// @Title: 两数之和 (Two Sum)
// @Author: qisiii
// @Date: 2024-04-10 21:52:24
// @Runtime: 2 ms
// @Memory: 43.9 MB
// @comment: 空间换时间，hashmap存储过往的key，检测target-num[i]是否存在
// @flag: BLUE
class Solution {
    public int[] twoSum(int[] nums, int target) {
        HashMap<Integer,Integer> old=new HashMap<>();
        for(int i=0;i<nums.length;i++){
            if(old.keySet().contains(target-nums[i])){
                return new int[]{i,old.get(target-nums[i])};
            }else{
                old.put(nums[i],i);
            }
        }
        return null;
    }
}

// @Title: 两数之和 (Two Sum)
// @Author: qisiii
// @Date: 2021-12-16 13:25:46
// @Runtime: 33 ms
// @Memory: 38.6 MB
// @comment: 暴力
// @flag: BLUE
class Solution {
    public int[] twoSum(int[] nums, int target) {
        int[] result= new int[2];
        for(int i=0;i<nums.length;i++){
            int cha=target-nums[i];
            for (int j = i+1; j < nums.length; j++) {
                if (cha==nums[j]){
                result[0]=i;
                result[1]=j;
                }
            }
        }
        return result;

    }
}