Casidoo-178

largestRectangularArea.js

// Given an array of integers representing the number of consecutive 1s immediately stacked vertically at this index
// calculate the largest area by grabbing the largest of all rectangular areas calculated at each index.
let largestRowArea = row => {
  let largestArea = 0;
  row.forEach((value, i) => {
    let area = value;
    if (value != 0) {
      for(let j=i-1; j>=0; j--)  {
        if (row[j] < value) break;
        area += value;
      }
      for(j=i+1; j<row.length; j++) {
        if (row[j] < value) break;
        area += value;
      }
    }
    if (area > largestArea) largestArea = area;
  })
  return largestArea
}

// We test our helper function
let rowAreaTests = [
  [[0,0,0,0,0,0,1],1],
  [[0,1,1,0,1,1,1],3],
  [[0,1,2,2,4,0],6],
  [[0,1,2,2,4,4],8]
]
rowAreaTests.map(([test, expected]) => largestRowArea(test) === expected ? "PASS" : "FAIL")
// OUTPUT: [ 'PASS', 'PASS', 'PASS', 'PASS' ]

// Calculate largest rectangular area in a matrix by first calculating the commulative row (with 0 zeroing out rows, and 1's
// being added to the previous total), then using the resulting row to caluculate the largestRow area, and returning the largest one of those
let getLargestRectangularArea = matrix => {
  let largestArea = 0;
  let currentAccumulatedRow = null;
  matrix.forEach((row, rowIndex) => {
    let intRow = row.map(s => +s);
    if (currentAccumulatedRow) {
      currentAccumulatedRow = currentAccumulatedRow.map((value, i) => intRow[i] ? value + intRow[i] : 0)
    } else {
      currentAccumulatedRow = [...intRow];
    }
    let localLargestArea = largestRowArea(currentAccumulatedRow);
    if (localLargestArea > largestArea) largestArea = localLargestArea;
  })
  return largestArea;
}

// Tests of solution
let tests = [
  [[
  ["1","1","1","0","0"],
  ["1","0","1","1","1"],
  ["1","1","0","1","1"],
  ["1","0","0","1","0"]
  ], 4],
  [[
  ["1","1","1","1","1"],
  ["1","0","1","1","1"],
  ["1","1","0","1","1"],
  ["1","0","0","1","0"]
  ], 6],
  [[
  ["1","1","1","1","1"],
  ["1","0","1","1","1"],
  ["1","1","1","1","1"],
  ["1","0","0","1","0"]
  ], 9],
  [[
  ["1","1","1","0","0"],
  ["1","1","1","1","1"],
  ["1","1","1","1","1"],
  ["1","0","0","1","0"]
  ], 10],
  [[
  ["0","0","0","0","0"],
  ["0","0","0","0","0"],
  ["0","0","0","0","0"],
  ["0","0","0","0","0"]
  ], 0],
  [[
  ["1","0","0","0","0"],
  ["0","0","0","0","0"],
  ["0","0","0","0","0"],
  ["0","0","0","0","0"]
  ], 1],
  [[
  ["1","1","1","1","1"],
  ["1","1","1","1","1"],
  ["1","1","1","1","1"],
  ["1","1","1","1","1"]
  ], 20],
]

tests.map(([test, expected]) => getLargestRectangularArea(test) === expected ? "PASS": "FAIL")
// OUTPUT: [
//  'PASS', 'PASS',
//  'PASS', 'PASS',
//  'PASS', 'PASS',
//  'PASS'
//]