Code deft interview questions

A title leetcode 168 & 171:

A, B, C, ..., Z, AA, AB, ..., AZ, BA, ..., ZZZ, AAAA .... find the i-th string

string solve(int num) {
    string ans;
    while(num--) { // 将0～25映射到‘A’～‘Z’
        int val = num%26;
        ans += 'A'+val;
        num /= 26;
    }
    reverse(ans.begin(), ans.end());
    return ans;
}

Title two

A known array size is N, the array b seek

B [I] = A [0] A [. 1] ... A [I. 1- A [I +. 1] ... A [. 1-N]
O (n-) time complexity, O (1) space complexity degree.
It requires removal cycle used i, no additional variables other memory.

void solve(int *a, int *b, int N) {
    int i;

    b[0] = 1;
    for(i = 1 ; i < N; i++)
        b[i] = b[i-1]*a[i-1];
    
    b[0] = a[--i];
    for(--i; i > 0; i--) {
        b[i] *= b[0];
        b[0] *= a[i];
    }
}