Solution.cpp

class Solution {
public:
    int findValidSplit(vector<int>& nums) {
        unordered_map<int, int> first;
        int n = nums.size();
        vector<int> last(n);
        iota(last.begin(), last.end(), 0);
        for (int i = 0; i < n; ++i) {
            int x = nums[i];
            for (int j = 2; j <= x / j; ++j) {
                if (x % j == 0) {
                    if (first.count(j)) {
                        last[first[j]] = i;
                    } else {
                        first[j] = i;
                    }
                    while (x % j == 0) {
                        x /= j;
                    }
                }
            }
            if (x > 1) {
                if (first.count(x)) {
                    last[first[x]] = i;
                } else {
                    first[x] = i;
                }
            }
        }
        int mx = last[0];
        for (int i = 0; i < n; ++i) {
            if (mx < i) {
                return mx;
            }
            mx = max(mx, last[i]);
        }
        return -1;
    }
};