The problem is asking to find all the starting indices of substrings in a given string that is a concatenation of every word in a given list of words exactly once. Each word in the list has the same length. If there are no such substrings, return -1.

Here is a step-by-step solution in Python:

1. First, define a function that takes a string and a list of words as parameters.

```python
def findSubstring(s, words):
```

2. Check if the list of words is empty. If it is, return an empty list.

```python
if not words:
return []
```

3. Calculate the length of a word and the total length of all words.

```python
wordLength = len(words[0])
totalLength = len(words) * wordLength
```

4. Initialize an empty list to store the starting indices of the substrings.

```python
indices = []
```

5. Iterate over the string. For each character, check if the substring starting at that character and having the total length of all words is a concatenation of the words. If it is, add the index to the list.

```python
for i in range(len(s) - totalLength + 1):
if sorted(s[i:i+totalLength:wordLength]) == sorted(words):
indices.append(i)
```

6. If the list of indices is empty, return -1. Otherwise, return the list.

```python
return indices if indices else -1
```

7. Call the function with the given string and list of words.

```python
print(findSubstring("dogcatcatcodecatdog", ["cat", "dog"])) # Output: [0, 13]
print(findSubstring("barfoobazbitbyte", ["dog", "cat"])) # Output: -1
```

This solution works by checking every possible substring of the given string that has the same length as the total length of all words. It sorts the characters in the substring and the words, and compares them. If they are equal, it means the substring is a concatenation of the words.

Question

The problem is asking to find all the starting indices of substrings in a given string that is a concatenation of every word in a given list of words exactly once. Each word in the list has the same length. If there are no such substrings, return -1.

Here is a step-by-step solution in Python:

1. First, define a function that takes a string and a list of words as parameters.

```python
def findSubstring(s, words):
```

2. Check if the list of words is empty. If it is, return an empty list.

```python
    if not words:
        return []
```

3. Calculate the length of a word and the total length of all words.

```python
    wordLength = len(words[0])
    totalLength = len(words) * wordLength
```

4. Initialize an empty list to store the starting indices of the substrings.

```python
    indices = []
```

5. Iterate over the string. For each character, check if the substring starting at that character and having the total length of all words is a concatenation of the words. If it is, add the index to the list.

```python
    for i in range(len(s) - totalLength + 1):
        if sorted(s[i:i+totalLength:wordLength]) == sorted(words):
            indices.append(i)
```

6. If the list of indices is empty, return -1. Otherwise, return the list.

```python
    return indices if indices else -1
```

7. Call the function with the given string and list of words.

```python
print(findSubstring("dogcatcatcodecatdog", ["cat", "dog"]))  # Output: [0, 13]
print(findSubstring("barfoobazbitbyte", ["dog", "cat"]))  # Output: -1
```

This solution works by checking every possible substring of the given string that has the same length as the total length of all words. It sorts the characters in the substring and the words, and compares them. If they are equal, it means the substring is a concatenation of the words.

Knowee AI · Accepted Answer