Angular (37) -- NgRx Effects

LeetCode Day 17: P136. Single Number (Easy)

题目：

一个整数的数组，所有数都是成对出现的，只有一个落单。找出这个落单的数。

Example 2:

Input: [4,1,2,1,2] Output: 4

我的思路：

用HashSet可以，但是成本太高。题目要求时间复杂度O(n), 并且不用额外的空间。所以也不可能每次都往前找一遍。放弃了，看答案。

最优解：

class Solution {
    public int singleNumber(int[] nums) {
      for(int i = 0; i < nums.length - 1; i++){
        nums[i+1] ^= nums[i];
      }
      return nums[nums.length-1];
    }
}

用XOR位运算，重复的都会被自动消掉。所以以后凡是遇到解决配对的问题，首先想想能否用XOR

Angular

Set navigation as a side effect

In the auth.effects.ts file, add a new effect.

@Effect({dispatch: false})
  authRedirect = this.actions$.pipe(
    ofType(AuthActions.AUTHENTICATE_SUCCESS),
    tap(() => {
      this.router.navigate(['/']);
    })
  );

This is an effect which does not dispatch a new action. It does not return a new observable. So we set the dispatch to false.

Display the error message

In the auth.component.ts file:

ngOnInit(): void {
    this.storeSub = this.store.select('auth').subscribe(authState => {
      this.isLoading = authState.loading;
      this.error = authState.authError;
      if (this.error) {
        this.showErrorAlert(this.error);
      }
    });
  }

In the auth.effects.ts file, we need to return our action.

const handleError = (errorRes: any) => {
  let errorMessage = 'An unknown error occured!';
  if (!errorRes.error || !errorRes.error.error) {
    return of(new AuthActions.AuthenticateFail(errorMessage));
  }
  switch (errorRes.error.error.message) {
    case 'EMAIL_EXISTS':
      errorMessage = 'This email exists already';
      break;
    case 'EMAIL_NOT_FOUND':
      errorMessage = 'This email does not exist';
      break;
    case 'INVALID_PASSWORD':
      errorMessage = 'This password is not correct.';
      break;
  }
  return of(new AuthActions.AuthenticateFail(errorMessage));
};

catchError(errorRes => {
            return handleError(errorRes);
          })