LeetCode 303 Range Sum Query - Immutable
概述
https://leetcode.com/problems/range-sum-query-immutable/
暴力遍历法
class NumArray {
public:
vector<int>* nums;
NumArray(vector<int>& nums) {
this->nums = &nums;
}
int sumRange(int left, int right) {
int sum = 0;
for (int i = left; i <= right; i ++ ) {
sum += nums->at(i);
}
return sum;
}
};
预计算前缀和
以下代码导致：runtime error: addition of unsigned offset to 0x6030000002e0 overflowed to 0x6030000002dc (stl_vector.h)
class NumArray {
public:
vector<int> sums;
NumArray(vector<int>& nums) {
sums.push_back(nums[0]);
for (int i = 1; i < nums.size(); i ++) {
sums.push_back(sums[i - 1] + nums[i]);
}
}
int sumRange(int left, int right) {
int lsum = 0 ? left == 0 : sums[left - 1];
return sums[right] - lsum;
}
};
这是因为三元运算符写错了，Python 写多了淦，应该是 int lsum = left == 0 ? 0 : sums[left - 1]，绝了，看了半天没看出问题来。