Problem: 1732. 找到最高海拔

题目描述

思路及解法

1.求取数组gain的大小$n$;
2.定义一个大小为$n+1$的数组preSum;
3.先求取前$n$个元素的前缀和，再最后单独处理preSum[n];其中preSum[n] = preSum[n - 1] + gain[n - 1];
4.求取处preSum中的最大元素；

复杂度

时间复杂度:

$O(n)$

空间复杂度:

$O(n)$

Code

class Solution {
public:
    /**
     * Prefix sum
     * 
     * @param gain Given array
     * @return int
     */
    int largestAltitude(vector<int>& gain) {
        int n = gain.size();
        vector<int> preSum(n + 1);
        int curSum = 0;
        for (int i = 0; i < n; ++i) {
            preSum[i] = curSum;
            curSum += gain[i];
        }
        preSum[n] = preSum[n - 1] + gain[n - 1];
        int maxRes = INT_MIN;
        for (int i = 0; i < n + 1; ++i) {
            maxRes = max(maxRes, preSum[i]);
        }
        return maxRes;
    }
};