3355. Zero Array Transformation I

You are given an integer array nums of length n and a 2D array queries, where queries[i] = [li, ri].

For each queries[i]:

• Select a subset of indices within the range [li, ri] in nums.
• Decrement the values at the selected indices by 1.

A Zero Array is an array where all elements are equal to 0.

Return true if it is possible to transform nums into a Zero Array after processing all the queries sequentially, otherwise return false.

A subset of an array is a selection of elements (possibly none) of the array.

class Solution {
public:
    bool isZeroArray(vector<int>& nums, vector<vector<int>>& queries) {
        vector<int> pre(nums.size() + 1);
        for(auto& q : queries) {
            pre[q[0]]++;
            pre[q[1] + 1]--;
        }
        for(int i = 0; i < nums.size(); i++) {
            if(i) pre[i] += pre[i-1];
            nums[i] -= pre[i];
            if(nums[i] > 0) return false;
        }
        return true;
    }
};