Problem: Shortest path in a grid between multiple point with a constraint
Problem description:
I'm trying to solve a problem on the internet and I wasn't able to pass all testcases, well, because my logic is flawed and incorrect. The flaw: I assumed starting to the closest 'F' point will get me to the shortest paths always, at all cases.
Thinks I thought of:
- Turning this into a graph problem and solve it based on it. > don't think this would work because of the constraint?
- Try to obtain all possible solution combinations > does not scale, if !8 combination exist.
#include <iostream>
#include <utility>
#include <string>
#include <vector>
#include <queue>
using namespace std;
#define N 4
#define M 4
int SearchingChallenge(string strArr[], int arrLength) {
int n = arrLength, m = n, steps = 0, food = 0;
// initial position of charlie
int init_j = 0;
int init_i = 0;
queue<pair<int,int>> q;
// directions
vector<int> offsets = {0,-1,0,1,0};
vector<pair<int,int>> food_nodes;
//store visited nodes, no need for extra work to be done.
int visited_nodes[4][4] = {{0}};
// get number of food pieces
for(int i = 0; i < m; i++){
for(int j = 0; j < n ; j++){
if(strArr[i][j] == 'F')
{
food++;
}
if(strArr[i][j] == 'C')
{
strArr[i][j] = 'O';
food_nodes.push_back({i,j});
}
}
}
while(food_nodes.size()>0){
food_nodes.erase(food_nodes.begin());
int break_flag=0;
q.push(food_nodes[0]);
while(!q.empty()){
int size = q.size();
while(size-->0){
pair<int,int> p = q.front();
q.pop();
for(int k = 0; k < 4; k++){
int ii = p.first + offsets[k], jj = p.second + offsets[k+1];
/* if(ii == 0 && jj == 3)
printf("HI"); */
if(jj >= 0 && jj < 4 && ii < 4 && ii >=0){
if(strArr[ii][jj] == 'F'){
strArr[ii][jj] = 'O';
while(!q.empty())
q.pop();
break_flag=1;
food--;
food_nodes.push_back({ii,jj});
break;
}
if(strArr[ii][jj] == 'O')
q.push({ii,jj});
if(strArr[ii][jj] == 'H' && food == 0)
return ++steps;
}
}
if(break_flag==1)
break;
}
steps++;
if(break_flag==1)
break;
}
}
return 0;
}
int main(void) {
// keep this function call here
/* Note: In C++ you first have to initialize an array and set
it equal to the stdin to test your code with arrays. */
//passing testcase
//string A[4] = {"OOOO", "OOFF", "OCHO", "OFOO"};
//failing testcase
string A[4] = {"FOOF", "OCOO", "OOOH", "FOOO"}
int arrLength = sizeof(A) / sizeof(*A);
cout << SearchingChallenge(A, arrLength);
return 0;
}
Your help is appreciated.
I have wrote the javascript solution for the mentioned problem..
function SearchingChallenge(strArr) {
// create coordinate array
const matrix = [
[0, 0], [0, 1], [0, 2], [0, 3],
[1, 0], [1, 1], [1, 2], [1, 3],
[2, 0], [2, 1], [2, 2], [2, 3],
[3, 0], [3, 1], [3, 2], [3, 3]
]
// flatten the strArr
const flattenArray = flatten(strArr)
// segreagate and map flattenArray with matrix to get coordinate of food,charlie and home
const segregatedCoordinates = flattenArray.reduce((obj, char, index) => {
if (char === 'F') obj['food'].push(matrix[index])
else if (char === 'C') obj['dog'] = matrix[index]
else if (char === 'H') obj['home'] = matrix[index]
return obj
}, { "food": [], dog: null, home: null })
// construct possible routes by permutating food coordinates
let possibleRoutes = permuate(segregatedCoordinates['food'])
// push dog and home in possibleRoutes at start and end positions
possibleRoutes = possibleRoutes.map((route) => {
return [segregatedCoordinates['dog'], ...route, segregatedCoordinates['home']]
})
// Calculate distances from every possible route
const distances = possibleRoutes.reduce((distances, route) => {
let moveLength = 0
for (let i = 0; i < route.length - 1; i++) {
let current = route[i], next = route[i + 1]
let xCoordinatePath = current[0] > next[0] ? (current[0] - next[0]) : (next[0] - current[0])
let yCoordinatePath = current[1] > next[1] ? (current[1] - next[1]) : (next[1] - current[1])
moveLength += xCoordinatePath + yCoordinatePath
}
distances.push(moveLength)
return distances
}, [])
return Math.min(...distances);
}
function permuate(arr) {
if (arr.length <= 2) return (arr.length === 2 ? [arr, [arr[1], arr[0]]] : arr)
return arr.reduce((res, ele, index) => {
res = [...res, ...permuate([...arr.slice(0, index), ...arr.slice(index + 1)]).map(val => [ele, ...val])]
return res
}, [])
}
function flatten(inputtedArr) {
return inputtedArr.reduce((arr, row) => {
arr = [...arr, ...row]
return arr
}, [])
}
console.log(SearchingChallenge(['FOOF', 'OCOO', 'OOOH', 'FOOO']));