Angular (44) -- Store Recipes via Effects

LeetCode Day 24: P169. Majority Element (Easy)

题目：

给一个长度为n的数组，找出重复次数最多的那个数，重复次数多于n/2。

我的思路:

首先想到的是HashMap。但是为了性能，尽可能不用。没想到什么好办法，直接看答案了。

Discuss:

class Solution {
    public int majorityElement(int[] array) {
        int count = 0;
        Integer candidate = null;

        for (int num : array) {
            if (count == 0) { // no majority element in prefix
                candidate = num; // selects new candidate majority element
            }
            count += (num == candidate) ? 1 : -1;
        }

        return candidate;
    }
}

并非最快的。

最优解：

class Solution {
    public int majorityElement(int[] nums) {
        Arrays.sort(nums);
        return nums[nums.length/2];
    }
}

把数组排个序，中点位置上的数一定是那个大数。

Angular:

Add a new Action, StoreRecipes

export const STORE_RECIPES = '[Recipe] Store Recipes';

export class StoreRecipes implements Action {
  readonly type = STORE_RECIPES;
}

Add a new effect, storeRecipes

@Effect({dispatch: false})
  storeRecipes = this.actions$.pipe(
    ofType(RecipesActions.STORE_RECIPES),
    withLatestFrom(this.store.select('recipes')),
    switchMap(([actionData, recipesState]) => {
      return this.http
        .put(
          'https://recipebook-cc2b1.firebaseio.com/recipes.json',
          recipesState.recipes
        );
    })
  );

withLatestFrom merges a value from another observable into this observable.