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| class Solution {
public:
void combination(string digits, vector<vector<char> >chars, vector<string>& ans, int len, int cur,int nums[], int sequence[], bool isUsed[][4]) {
for(int i = 0;i < nums[digits[cur] - '0'];i++) {
if(isUsed[cur][i] == false) {
isUsed[cur][i] = true;
vector<char> temp = chars[digits[cur] - '0' - 2];
sequence[cur] = temp[i];
if(cur == digits.length() - 1) {
string str = "";
for(int j = 0;j < digits.length();j++) {
str += sequence[j];
}
ans.push_back(str);
} else {
combination(digits, chars, ans, len, cur + 1, nums, sequence, isUsed);
}
isUsed[cur][i] = false;
}
}
}
vector<string> letterCombinations(string digits) {
vector<string> ans;
if(digits.length() == 0) {
return ans;
}
vector<vector<char> >chars;
int nums[10] = {0, 0, 3, 3, 3, 3, 3, 4, 3, 4};
int index = 0;
for(int i = 2;i < 10;i++) {
vector<char> temp;
for(int j = 0;j < nums[i];j++, index++) {
char ch = 'a' + index;
temp.push_back(ch);
}
chars.push_back(temp);
}
bool isUsed[digits.length()][4] = {{0}};
int sequence[digits.length()] = {0};
combination(digits, chars, ans, digits.length(), 0, nums, sequence, isUsed);
return ans;
}
};
|
