g0101_0200.s0119_pascals_triangle_ii.Solution Maven / Gradle / Ivy

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Java-based LeetCode algorithm problem solutions, regularly updated

There is a newer version: 1.37

package g0101_0200.s0119_pascals_triangle_ii;

// #Easy #Array #Dynamic_Programming #Dynamic_Programming_I_Day_12
// #2022_02_22_Time_0_ms_(100.00%)_Space_41.9_MB_(14.49%)

import java.util.ArrayList;
import java.util.List;

public class Solution {
    public List getRow(int rowIndex) {
        int[] buffer = new int[rowIndex + 1];
        buffer[0] = 1;
        computeRow(buffer, 1);
        // Copy buffer to List of Integer.
        List ans = new ArrayList<>(buffer.length);
        for (int i = 0; i < buffer.length; i++) {
            ans.add(buffer[i]);
        }
        return ans;
    }

    private void computeRow(int[] buffer, int k) {
        if (k >= buffer.length) {
            return;
        }
        int previous = buffer[0];
        for (int i = 1; i < k; i++) {
            int tmp = previous + buffer[i];
            previous = buffer[i];
            buffer[i] = tmp;
        }
        buffer[k] = 1;
        computeRow(buffer, k + 1);
    }
}