2750. Ways to Split Array Into Good Subarrays

Description

You are given a binary array nums.

A subarray of an array is good if it contains exactly one element with the value 1.

Return an integer denoting the number of ways to split the array nums into good subarrays. As the number may be too large, return it modulo 109 + 7.

A subarray is a contiguous non-empty sequence of elements within an array.

 

Example 1:

Input: nums = [0,1,0,0,1]
Output: 3
Explanation: There are 3 ways to split nums into good subarrays:
- [0,1] [0,0,1]
- [0,1,0] [0,1]
- [0,1,0,0] [1]

Example 2:

Input: nums = [0,1,0]
Output: 1
Explanation: There is 1 way to split nums into good subarrays:
- [0,1,0]

 

Constraints:

  • 1 <= nums.length <= 105
  • 0 <= nums[i] <= 1

Solutions

Solution 1

Python Code
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class Solution:
    def numberOfGoodSubarraySplits(self, nums: List[int]) -> int:
        mod = 10**9 + 7
        ans, j = 1, -1
        for i, x in enumerate(nums):
            if x == 0:
                continue
            if j > -1:
                ans = ans * (i - j) % mod
            j = i
        return 0 if j == -1 else ans

Java Code
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class Solution {
    public int numberOfGoodSubarraySplits(int[] nums) {
        final int mod = (int) 1e9 + 7;
        int ans = 1, j = -1;
        for (int i = 0; i < nums.length; ++i) {
            if (nums[i] == 0) {
                continue;
            }
            if (j > -1) {
                ans = (int) ((long) ans * (i - j) % mod);
            }
            j = i;
        }
        return j == -1 ? 0 : ans;
    }
}

C++ Code
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class Solution {
public:
    int numberOfGoodSubarraySplits(vector<int>& nums) {
        const int mod = 1e9 + 7;
        int ans = 1, j = -1;
        for (int i = 0; i < nums.size(); ++i) {
            if (nums[i] == 0) {
                continue;
            }
            if (j > -1) {
                ans = 1LL * ans * (i - j) % mod;
            }
            j = i;
        }
        return j == -1 ? 0 : ans;
    }
};

Go Code
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func numberOfGoodSubarraySplits(nums []int) int {
	const mod int = 1e9 + 7
	ans, j := 1, -1
	for i, x := range nums {
		if x == 0 {
			continue
		}
		if j > -1 {
			ans = ans * (i - j) % mod
		}
		j = i
	}
	if j == -1 {
		return 0
	}
	return ans
}

TypeScript Code
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function numberOfGoodSubarraySplits(nums: number[]): number {
    let ans = 1;
    let j = -1;
    const mod = 10 ** 9 + 7;
    const n = nums.length;
    for (let i = 0; i < n; ++i) {
        if (nums[i] === 0) {
            continue;
        }
        if (j > -1) {
            ans = (ans * (i - j)) % mod;
        }
        j = i;
    }
    return j === -1 ? 0 : ans;
}

C# Code
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public class Solution {
    public int NumberOfGoodSubarraySplits(int[] nums) {
        long ans = 1, j = -1;
        int mod = 1000000007;
        int n = nums.Length;
        for (int i = 0; i < n; ++i) {
            if (nums[i] == 0) {
                continue;
            }
            if (j > -1) {
                ans = ans * (i - j) % mod;
            }
            j = i;
        }
        return j == -1 ? 0 : (int) ans;
    }
}