Matrix Search Sequel - Amazon Top Interview Questions

Problem Statement :

Given a two-dimensional integer matrix, where every row and column is sorted in ascending order, return whether an integer target exists in the matrix.

This should be done in \mathcal{O}(n + m)O(n+m) time.


n, m ≤ 250 where n and m are the number of rows and columns in matrix

Example 1


matrix = [
    [1, 3, 9],
    [2, 5, 10],
    [5, 7, 13]

target = 7



Solution :


                        Solution in C++ :

bool solve(vector<vector<int>>& matrix, int target) {
    int n = matrix.size();
    int m = matrix[0].size();
    int i = 0;
    int j = m - 1;
    while (i < n && j >= 0) {
        if (matrix[i][j] == target)
            return true;
        else if (matrix[i][j] > target)
    return false;

                        Solution in Java :

import java.util.*;

class Solution {
    public boolean solve(int[][] matrix, int target) {
        for (int row = 0; row < matrix.length; row++) {
            int idx = Arrays.binarySearch(matrix[row], target);
            if (idx < 0)
                return true;

        return false;

                        Solution in Python : 
class Solution:
    def found(self, row, target):
        lo = 0
        hi = len(row)

        while lo <= hi:
            mid = lo + (hi - lo) // 2
            if row[mid] == target:
                return True
            elif target < row[mid]:
                hi = mid - 1
                lo = mid + 1

        return False

    def solve(self, matrix, target):
        for row in matrix:
            if row[0] <= target and row[-1] >= target:
                if self.found(row, target):
                    return True
        return False

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