LeetCode-Solutions/C++/longest-balanced-subarray-i.cpp at master · kamyu104/LeetCode-Solutions · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
// Time:  O(nlogn)
// Space: O(n)

// segment tree, binary search, prefix sum
class Solution {
public:
    int longestBalanced(vector<int>& nums) {
        const int n = size(nums) + 1;
        SegmentTree st(n);
        int result = 0;
        unordered_map<int, int> lookup;
        for (int i = 1, curr = 0; i <= size(nums); ++i) {
            const auto& d = nums[i - 1] & 1 ? +1 : -1;
            if (lookup.count(nums[i - 1])) {
                st.update(lookup[nums[i - 1]], n - 1, -d);
                curr -= d;
            }
            curr += d;
            lookup[nums[i - 1]] = i;
            st.update(lookup[nums[i - 1]], n - 1, +d);
            const auto& l = i - st.binary_search(curr);
            if (l > result) {
                result = l;
            }
        }
        return result;
    }

private:
    class SegmentTree {
    public:
        explicit SegmentTree(int N)
         :  base_(N > 1 ? 1 << (__lg(N - 1) + 1) : 1),
            lazy_(base_),
            min(N > 1 ? 1 << (__lg(N - 1) + 2) : 2),
            max(N > 1 ? 1 << (__lg(N - 1) + 2) : 2) {

        }

        void update(int L, int R, const int val) {
            L += base_;
            R += base_;
            int L0 = L, R0 = R;
            for (; L <= R; L >>= 1, R >>= 1) {
                if ((L & 1) == 1) {
                    apply(L++, val);
                }
                if ((R & 1) == 0) {
                    apply(R--, val);
                }
            }
            pull(L0);
            pull(R0);
        }

        int binary_search(int x) {
            int i = 1;
            while (!(i >= base_)) {
                if (lazy_[i]) {
                    apply(i << 1, lazy_[i]);
                    apply((i << 1) | 1, lazy_[i]);
                    lazy_[i] = 0;
                }
                i <<= 1;
                if (!(min[i] <= x && x <= max[i])) {
                    i |= 1;
                }
            }
            return i - base_;
        }

        vector<int> min, max;

    private:
        void apply(int x, const int val) {
            min[x] += val;
            max[x] += val;
            if (x < base_) {
                lazy_[x] += val;
            }
        }

        void pull(int x) {
            while (x > 1) {
                x >>= 1;
                min[x] = min[x << 1] < min[(x << 1) | 1] ? min[x << 1] : min[(x << 1) | 1];
                max[x] = max[x << 1] > max[(x << 1) | 1] ? max[x << 1] : max[(x << 1) | 1];
                if (lazy_[x]) {
                    min[x] += lazy_[x];
                    max[x] += lazy_[x];
                }
            }
        }

        void push(int x) {
            for (int h = __lg(x) - 1; h > 0; --h) {
                int y = x >> h;
                if (lazy_[y]) {
                    apply(y << 1, lazy_[y]);
                    apply((y << 1) | 1, lazy_[y]);
                    lazy_[y] = 0;
                }
            }
        }

        int base_;
        vector<int> lazy_;
    };
};

// Time:  O(n^2)
// Space: O(n)
// brute force
class Solution2 {
public:
    int longestBalanced(vector<int>& nums) {
        int result = 0;
        for (int left = 0; left < size(nums); ++left) {
            unordered_set<int> lookup;
            for (int right = left, curr = 0; right < size(nums); ++right) {
                if (!lookup.count(nums[right])) {
                    lookup.emplace(nums[right]);
                    curr += nums[right] & 1 ? +1 : -1;
                }
                if (curr == 0) {
                    result = max(result, right - left + 1);
                }
            }
        }
        return result;
    }
};