---
title: leetcode 927
tags: leetcode, math
---

// https://leetcode.com/problems/three-equal-parts/
class Solution {
public:
    vector<int> threeEqualParts(vector<int>& A) {
        int ary[30000] = {0};
        int cnt = 0, f1 = -1;
        for (int i=0; i<A.size(); i++) {
            if (f1 < 0 && A[i] == 1) f1=i;
            if (A[i]) ary[cnt++] = i;
        }
        if (cnt==0) return {0, 2};
        for (int i=0; i<cnt-1; i++) {
            ary[i] = ary[i+1] - ary[i];
        }
        ary[cnt-1] = A.size() - ary[cnt-1];
        if (cnt % 3) return {-1, -1};
        int i = 0;
        int x=f1, y=f1;
        int tmp = cnt/3 - 1;
        for (i=0; i<tmp; i++) {
            x += ary[i];
            y += ary[i] + ary[tmp + 1 + i];
            if (ary[i] != ary[tmp + 1 + i] || ary[i] != ary[tmp*2 + 2 + i])
                break;
        }
        cout << i << endl;
        if (i != tmp) return {-1, -1};
        cout << ary[tmp] << " " << ary[cnt-1] <<" " << ary[tmp*2 + 1] << endl;
        if (ary[tmp] < ary[cnt-1] || ary[tmp * 2 + 1] < ary[cnt-1]) return {-1, -1};
        return {x + ary[cnt-1]-1, y + ary[tmp] + ary[cnt-1]};
    }
};