Spiral Matrix II

Given a positive integer n, generate a square matrix filled with elements from 1 to n2 in spiral order.

Example:

Input: 3 Output: [ [ 1, 2, 3 ], [ 8, 9, 4 ], [ 7, 6, 5 ] ]

Solution:

    vector<vector<int>> generateMatrix(int n) {
        vector<vector<int>> ans(n, vector<int>(n, 0));
        int rLow = 0, rHigh = n-1;
        int cLow = 0, cHigh = n-1;
        int dir = 0, val = 1;

        while (rLow <= rHigh && cLow <= cHigh) {
            if (dir == 0) {
                // right
                for (int i=cLow; i<=cHigh; i++) {
                    ans[rLow][i] = val; val += 1;
                }
                rLow += 1;
            } else if (dir == 1) {
                // down
                for (int i=rLow; i<=rHigh; i++) {
                    ans[i][cHigh] = val; val += 1;
                }
                cHigh -= 1;
            } else if (dir == 2) {
                // left
                for (int i=cHigh; i>=cLow; i--) {
                    ans[rHigh][i] = val; val += 1;
                }
                rHigh -= 1;
            } else {
                // up
                for (int i=rHigh; i>=rLow; i--) {
                    ans[i][cLow] = val; val += 1;
                }
                cLow += 1;
            }
            dir = (dir + 1) % 4;
        }

        return ans;
    }