题解 | 喜欢切数组的红

#include <iostream>
#include <vector>
using namespace std;

int main() {
    int n;
    cin >> n;
    vector<int> data(n);
    vector<int64_t> sum(n);
    vector<int> pCnt(n);
    int64_t s = 0;
    int64_t p = 0;
    for(auto i = 0; i < n; ++i) {
        cin >> data[i];
        s += data[i];
        sum[i] = s;
        if(data[i] > 0) {
            p++;
        }
        pCnt[i] = p;
    }
    if(s%3 != 0) {
        cout << 0 << endl;
        return 0;
    }
    auto avg = s/3;
    int cnt = 0;
    for(auto i = 0; i < n-2; ++i) {
        if(sum[i] != avg || pCnt[i] == 0 ) {
            continue;
        }
        int lastP = pCnt[i];
        for(auto j = i + 1; j < n-1; ++j) {
            if(sum[j] != 2*avg || pCnt[j] - lastP == 0 ) {
                continue;
            }
            cnt++;
        }
    }
    cout << cnt << endl;
}
// 64 位输出请用 printf("%lld")