---
tags: leetcode
---

# [777. Swap Adjacent in LR String](https://leetcode.com/problems/swap-adjacent-in-lr-string/)
---
# My Solution
## The Key Idea for Solving This Coding Question
## C++ Code

class Solution {
public:
    bool canTransform(string start, string end) {
        string startNoX, endNoX;
        removeX(start, startNoX);
        removeX(end, endNoX);
        if (startNoX != endNoX) {
            return false;
        }

        vector<int> startLIdx, endLIdx;
        getIndices(start, end, startLIdx, endLIdx, 'L');
        for (int i = 0; i < startLIdx.size(); ++i) {
            if (endLIdx[i] > startLIdx[i]) {
                return false;
            }
        }

        vector<int> startRIdx, endRIdx;
        getIndices(start, end, startRIdx, endRIdx, 'R');
        for (int i = 0; i < startRIdx.size(); ++i) {
            if (endRIdx[i] < startRIdx[i]) {
                return false;
            }
        }

        return true;
    }

private:
    void removeX(string &s, string &noX) {
        for (auto &c : s) {
            if (c != 'X') {
                noX.push_back(c);
            }
        }
    }

    void getIndices(string &start, string &end, 
                    vector<int> &startIdx, vector<int> &endIdx, char c) {
        for (int i = 0; i < start.size(); ++i) {
            if (start[i] == c) {
                startIdx.push_back(i);
            }
            if (end[i] == c) {
                endIdx.push_back(i);
            }
        }
    }
};

### Time Complexity
### Space Complexity
## C++ Code 2

class Solution {
public:
    bool canTransform(string start, string end) {
        string startNoX, endNoX;
        removeX(start, startNoX);
        removeX(end, endNoX);
        if (startNoX != endNoX) {
            return false;
        }
        
        vector<int> startRIdx, startLIdx, endRIdx, endLIdx;
        for (int i = 0; i < start.size(); ++i) {
            if (start[i] == 'R') {
                startRIdx.push_back(i);
            } else if (start[i] == 'L') {
                startLIdx.push_back(i);
            }
            if (end[i] == 'R') {
                endRIdx.push_back(i);
            } else if (end[i] == 'L') {
                endLIdx.push_back(i);
            }
        }
        
#if 1
        for (int i = 0; i < startRIdx.size(); ++i) {
            if (startRIdx[i] > endRIdx[i]) {
                return false;
            }
        }
#endif

        for (int i = 0; i < startLIdx.size(); ++i) {
            if (startLIdx[i] < endLIdx[i]) {
                return false;
            }
        }
        
        return true;
    }
    
private:
    void removeX(string &org, string &noX) {
        for (char &c : org) {
            if (c != 'X') {
                noX.push_back(c);
            }
        }
    }

};

# Miscellaneous
<!--
# Test Cases

"RXXLRXRXL"
"XRLXXRRLX"

"X"
"L"

* Wrong Answer

"RL"
"LR"

* Wrong Answer

"XXXXXLXXXX"
"LXXXXXXXXX"

* Wrong Answer

"LXXLXRLXXL"
"XLLXRXLXLX"

* Wrong Answer

"XXXXXLXXXLXXXX"
"XXLXXXXXXXXLXX"

* Other test cases

"RLX"
"XLR"

-->