LeetCode/Java/473.java at master · strengthen/LeetCode · 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
__________________________________________________________________________________________________
sample 1 ms submission
class Solution {
    public boolean makesquare(int[] nums) {
        if (nums.length == 0) {
            return false;
        }
        int sum = 0;
        int max = Integer.MIN_VALUE;
        for (int i : nums) {
            sum += i;
            max = Math.max(max, i);
        }

        if (sum % 4 != 0 || max > sum / 4) {
            return false;
        }

        int edge = sum / 4;
        boolean[] visited = new boolean[nums.length];
        Arrays.sort(nums);
        visited[nums.length - 1] = true;
        return dfs(nums, edge, visited, nums[nums.length-1], 0, nums.length-1);
    }

    private boolean dfs(int[] nums, int edge, boolean[] visited, int currentSum, int found, int left) {

        if (currentSum == edge) {
            currentSum = 0;
            found++;
        }

        if (left == 0 || found == 4) {
            if (left == 0 && found == 4 && currentSum == 0) {
                return true;
            } else {
                return false;
            }
        }

        for (int i = nums.length - 1; i >= 0; i--) {
            if (visited[i]) {
                continue;
            }
            if(currentSum + nums[i] > edge) {
                continue;
            } else {
                int currentSum_new = currentSum;
                int found_new = found;
                int left_new = left - 1;
                if(currentSum + nums[i] == edge) {
                    currentSum_new = 0;
                    found_new++;
                } else {
                    currentSum_new += nums[i];
                }
                visited[i] = true;

                if (dfs(nums, edge, visited, currentSum_new, found_new, left_new)) {
                    return true;
                }

                visited[i] = false;
            }
        }

        return false;
    }
}
__________________________________________________________________________________________________
sample 2 ms submission
class Solution {
    boolean helper(int[] nums, int group, boolean[] visited, int target, int curSum, int start) {
        if (group == 3) return true;
        if (curSum > target) return false;
        if (curSum == target) return helper(nums, group+1, visited, target, 0, 0);

        for (int i = start; i < nums.length; i++) {
            if (visited[i] == true) continue;
            if (i > 0 && nums[i] == nums[i-1] && !visited[i-1]) continue;
            visited[i] = true;
            if (helper(nums, group, visited, target, curSum+nums[i], i+1)) return true;
            visited[i] = false;
        }

        return false;
    }

    public boolean makesquare(int[] nums) {
        if (nums == null || nums.length < 4) return false;
        int sum = 0;
        for (int num: nums) sum += num;
        if (sum % 4 != 0) return false;

        return helper(nums, 0, new boolean[nums.length], sum / 4, 0, 0);
    }
}
__________________________________________________________________________________________________
sample 33512 kb submission
class Solution {
    public boolean makesquare(int[] nums) {
        if (nums == null || nums.length == 0) return false;
        int sum = Arrays.stream(nums).sum();
        if (sum % 4 != 0) return false;
        int length = sum / 4;
        boolean[] visited = new boolean[nums.length];
        return dfs(nums, length, visited, 0, 0, 0);
    }

    private boolean dfs(int[] nums, int length, boolean[] visited,
                        int cur, int start, int count) {
        if (count == 4) {
            for (int i = 0; i < nums.length; i++) {
                if (!visited[i]) return false;
            }
            return true;
        } else if (cur > length) {
            return false;
        } else if (cur == length) {
            return dfs(nums, length, visited, 0, 0, count+1);
        } else {
            for (int i = start; i < nums.length; i++) {
                if (visited[i]) continue;
                visited[i] = true;
                if (dfs(nums, length, visited, cur+nums[i], i+1, count)) return true;
                visited[i] = false;
            }
            return false;
        }
    }
}