leetcode_881_救生艇

思路一

考虑对数组进行排序,然后利用对撞指针来完成操作.

class Solution {
public:
    int numRescueBoats(vector<int>& people, int limit) {
        quickSort(people, 0, people.size() - 1);
        // 设置对撞指针
        int left = 0, right = people.size() - 1 ;
        int res = 0;
        while(left <= right) {
          if(left == right) {
            res++;
            break;
          }
          if (people[left] + people[right] > limit) {
            res++;
            right--;
          } else {
            res++;
            left++;
            right--;
          }
        }
        return res;
    }

    /**
    * @name: 
    * @msg: 利用此方法进行数组的分区,默认以数组的最后一个
    * @param {vector<int>} &array
    * @param {int} pivot
    * @param {int} right
    * @return {*}
    */
    int partition(vector<int> &array, int left, int right) {
        int pivot = array[right], index = left - 1;

        // 利用双指针进行交换
        for (int j = left; j < right; j++) {
        if(array[j] <= pivot) {
            index = index + 1;
            swap(array[index], array[j]);
        }
        }
        swap(array[index + 1], array[right]);
        return index + 1;
    }

    void quickSort(vector<int> &array, int left, int right) {
        if (left < right) {
        int middle = partition(array, 0, right);
        quickSort(array, 0 , middle - 1);
        quickSort(array, middle + 1, right);
        }

    }
};