Question

Write a C++ program to simulate a stream path.

In this problem you can make the following assumptions

1. The elevation grid will be a n row, m column grid of integers, where n and m are constant.

2. Once the stream origin location is specified, then the stream flows to whichever of the four adjacent locations in the grid represents the largest descent.

3. If more than one of the adjacent locations have the largest descent, then the water flows to whichever adjacent location appears first in the last item's list.

4. The process continues, with the stream flowing from location to location until it either reachers a location where none of the four adjacent locations has its elevation strictly less than that location, or until it reachesr the edge of the grid. (any row with index 0 or n-1 or any column with index 0 or n-1).

Write a C++ program that sets up a grid, and asks the user to input an initial location. If the input location is an invalid location, the program should print "Invalid location" to the screen. Otherwise the program should call a function:

bool moveToLowerElev(int elev[][m], int n, int m, int& r, int& c)

Given the row and column of the input location, this function should first check to see if that location is on the end of the grid. If it is, the function should return false. If it is not, the function should check the four adjacent locations. If none has an elevation strictly less than the current location, then the function should return false. Otherwise the function should return true, and return the row and column of the adjacent location with the leaset elevation through the reference parameters int& r and int& c.

If moveToLowerElev returns false, the main program should output "Path ends." Otherwise the program should print the new row and colum, as well as the elevation of the new location.

Use the grid int elev[n][m] = {0, 0, 0, 0, 0}

{0, 1, 2, 3, 4}

{0, 2, 0, 2, 0}

{2, 3, 1, 2, 4}

{3, 4, 3, 4, 5}

{4, 5, 5, 2, 6}

{3, 3, 3, 2, 1}

Here is an example of the program

Input the origin location (row and column): 4 3

Row 3, column 3, elevation 2

The moveToLowerElev should be defined after the main function.

Answer 1

#include <cstdlib>
#include <iostream>
#include <fstream>
using namespace std;

// function to find the min of two elements
int min(int a, int b) {
    return a>b?b:a;
}

bool moveToLowerElev(int **elev, int n, int m, int& r,int& c) {

    if(r < 0 || r >= n || c < 0 || c>= m) { // if the data is invalid
           cout<<"Invalid row or column"<<endl;
           return false;
    }
    if(r == 0 || r == n-1 || c == 0 || c == m-1) {// if we are at any border side
        cout<<"PathEnds."<<endl;
        return true; // we havefind the path, and it is at the end
    }
    // find the min elevation we would like togo
    int min_elev = min(elev[r-1][c],min(elev[r][c+1], min(elev[r+1][c], elev[r][c-1])));

    // if the min elevation is greater than thecurrent elevation
    if(elev[r][c] < min_elev) { // there is no,way to go
        cout<<"PathEnds."<<endl;
        return false; // returnfalse, as we can not find a way
    }

    if(min_elev == elev[r-1][c]) { // if the minelevation is the top, goto top
        cout<<"Row"<<(r-1)<<", column "<<(c)<<", elevation"<<elev[r-1][c]<<endl;
        returnmoveToLowerElev(elev, n, m, --r, c);
    } else if(min_elev == elev[r][c+1]) {// if themin elevation is the right, goto right
        cout<<"Row"<<(r)<<", column "<<(c+1)<<", elevation"<<elev[r][c+1]<<endl;
        returnmoveToLowerElev(elev, n, m, r, ++c);
    } else if(min_elev == elev[r+1][c]) { // if themin elevation is the bottom, goto bottom
        cout<<"Row"<<(r+1)<<", column "<<(c)<<", elevation"<<elev[r+1][c]<<endl;
        returnmoveToLowerElev(elev, n, m, ++r, c);
    } else { // if the min elevation is the left,goto left
        cout<<"Row"<<(r)<<", column "<<(c-1)<<", elevation"<<elev[r][c-1]<<endl;
        returnmoveToLowerElev(elev, n, m, r, --c);
    }
}

// function to read the data from a gove file
int** read(string filename, int& N, int &M) {
    ifstream in(filename.c_str()); // open the fileto read
    if(!in) { // if the file is not opened
        cout<<"FILE NOTFOUND"<<endl;
        exit(0);
    }

    int r, c;
    in>>r>>c; // read the dimensions ofthe grind first

    //cout<<"File contents are :"<<endl;
    //cout<<r<<""<<c<<endl;
    // create a grid
    int** grid = new int*[r];
    for(int i = 0; i < r; i++) {
        grid[i] = newint[c];
    }
    for(int i = 0; i < r; i++) {
        for(int j = 0; j < c;j++) {
           in>>grid[i][j];
           //cout<<grid[i][j]<<" ";
        }
       //cout<<endl;
    }
    N = r;
    M = c;
    in.close(); // close the file
    return grid; // return the grid
}

int main() {
string filename;
    cout<<"Enter the file name : ";
    cin >> filename;

    int N, M; // dimensions of the grid
    int** elev = read(filename, N, M);

    char ch = 'y';
    do {
        cout<<"Input theorigin location (row and column): ";
        int i, j;
        cin>> i>>j;// read the location from the user

        // find thepath
        moveToLowerElev(elev, N,M, i, j);

        // ask if he wants tocontinue
        cout<<"Enteranother origin location (y/n)? ";
        cin >> ch;

    } while(ch == 'y'); // while the user enters'y' continue the loop
return 0;
}

// OUTPUT