You are given a string, S, and a list of words, L, that are all of the same length. Find all starting indices of substring(s) in S that is a concatenation of each word in L exactly once and without any intervening characters. For example, given: S: "barfoothefoobarman" L: ["foo", "bar"] You should return the indices: [0,9]. (order does not matte…

leetcode_substring_with_concatenation_of_all_words.cpp

#define MAXN 10000
int f[MAXN];
int flag[MAXN];
int num[MAXN];

class Solution {
public:
    vector<int> findSubstring(string S, vector<string> &L) {
        memset(f, -1, sizeof(f));
        int m = S.length();
        int n = L.size();
        int len = L[0].length();
        for (int i = 0; i < m; ++i) {
            for (int j = 0; j < n; ++j) {
                bool match = true;
                for (int k = 0; k < len; ++k) 
                    if (L[j][k] != S[i + k]) {
                        match = false;
                        break;
                    }
                if (match) {
                    f[i] = j;
                    break;
                }
            }
        }
        memset(num, 0, sizeof(num));
        for (int i = 0; i < n; ++i) {
            if (num[i] != 0)
                continue;
            num[i]++;
            for (int j = i + 1; j < n; ++j)
                if (L[i] == L[j]) {
                    num[j]--;
                    num[i]++;
                }
        }
        vector<int> ans;
        for (int i = 0; i <= m - n * len; ++i) {
            memset(flag, 0, sizeof(flag));
            int cnt = 0;
            for (int j = 0; j < n; ++j) {
                int k = f[i + j * len];
                if (k != -1 && flag[k] < num[k]) {
                    flag[k]++;
                    cnt++;
                }
                else
                    break;
            }
            if (cnt == n)
                ans.push_back(i);
        }
        return ans;
    }
};