Leetcode candy中c++解法

/********************************************************************************** * * There are N children standing in a line. Each child is assigned a rating value. * * You are giving candies to these children subjected to the following requirements:* * Each child must have at least one candy.* Children with a higher rating get more candies than their neighbors.* * What is the minimum candies you must give?* *               **********************************************************************************/   此题解法很巧妙，首先将权重数组从做到又进行处理，只要大于前一个权重，则使得分配数加1   例如5, 6, 7, 4, 1, 2, 3, 2, 1, 7是一个权重数组   则  1  2  3  1  1  2  3  1  1  2   然后从右向左即可做出统计total的值#include <stdlib.h>#include <time.h>#include <iostream>#include <vector>using namespace std;void print(vector<int> &v);/* *    The soluiton is O(2n) run-time complexity * *    For example: * *        ratings[] = { 5, 6, 7, 4, 1, 2, 3, 2, 1, 7 }  * *    1) Go through the ratings from left to right. * *       Find the each increasing sub-array, giving the minimal candy      * *        ratings[] = { 5, 6, 7,   4,   1, 2, 3,   2,   1, 7 }  *                      ------>    ->   ------>    ->   ---> *          candy[] = { 1, 2, 3,   1,   1, 2, 3,   1,   1, 2 } * *    2) Go through the raings from right to left. * *             ratings[] = { 5,   6,   7, 4, 1,   2,   3, 2, 1,   7 }  *                           <-   <-   <------    <-   <------    <- *          prev_candy[] = { 1,   2,   3, 1, 1,   2,   3, 1, 1,   2 } *                                        +1              +1 *               candy[] = { 1,   2,   3, 2, 1,   2,   3, 2, 1,   2 } * *    3) total candy is 19 * */int candy(vector<int> &ratings) {    vector<int> candyCnt(ratings.size()) ;    //allocate candies, considering the minimal rating on the left    candyCnt[0] = 1;    for(int i = 1; i < ratings.size(); i++){        candyCnt[i] = ratings[i] > ratings[i-1] ? candyCnt[i-1]+1 : 1;    }    print(candyCnt);     //modify the allocation, considering the minimal rating on the right    int totalCandy = candyCnt[ratings.size()-1];    for(int i = ratings.size()-2; i >= 0; i--){        candyCnt[i] = (ratings[i] > ratings[i+1] && candyCnt[i+1]+1 > candyCnt[i]) ? candyCnt[i+1]+1 : candyCnt[i];        //count total candies by the way        totalCandy += candyCnt[i];    }    print(candyCnt);    return totalCandy;}void generateRatings(vector<int> &ratings, int n) {    srand(time(0));    for (int i=0; i<n; i++) {        ratings.push_back(rand()%10);    }}void print(vector<int> &v) {    for(int i=0; i<v.size(); i++){        cout << v[i] << " ";    }    cout << endl;}int main(int argc, char**argv){    int n = 10;    if (argc>1){        n = atoi(argv[1]);    }       vector<int> ratings;    generateRatings(ratings, n);    print(ratings);    cout << candy(ratings) << endl;    cout << "--------------------" << endl;    int r[] = { 5, 6, 7, 4, 1, 2, 3, 2, 1, 7 };    vector<int> ra(r, r+sizeof(r)/sizeof(r[0]));    print(ra);    cout << candy(ra) << endl;    return 0;}