Two-Dimensional Array Searching Algorithm Optimisation - c++

Question

I have been given a "Sand box" of variable length and width. I've been given instructions to find a "shovel" of static size, which may be oriented either horizontally or vertically. I implement the following algorithm in order to search the least amount of times to find one valid location (one which corresponds to a "part of the object") in the grid:
found = false;
nShift = 0;
shovelSize = 4;
for(int i = 0; i < SandBoxRows; i++) {
for(int j = 0; j < SandBoxColumns; j+=shovelSize) {
found = probeSandBoxTwo(('A' + i), (j + 1 + nShift));
}
if(nShift >= shovelSize - 1 || nShift > SandBoxColumns) {
nShift = 0;
} else {
nShift++;
}
}
In this case, the "Sand box" will be tested by the function as described below.
I completely recreate this scenario with a "Sand box" whose size is fixed (though easily manipulated) whose shovel is still randomly placed and oriented within the following code:
#include <cstdlib>
#include <ctime>
#include <iostream>
using namespace std;
const int ROW = 12;
const int COL = 16;
char sandbox[ROW][COL];
bool probeSandBoxTwo(char c, int i);
void displayResults(int sCount, bool found, int x, int y);
void displaySandbox();
void displaySearchPattern();
void fillSandbox();
void placeShovel();
int main() {
fillSandbox();
placeShovel();
displaySandbox();
//define your variables here
bool found;
int nShift,
sCount,
shovelSize,
x,
y;
found = false;
nShift = 0;
shovelSize = 4;
sCount = 0;
for(int i = 0; i < ROW && !found; i++) {
for(int j = 0; j < COL && !found; j+=shovelSize) {
found = probeSandBoxTwo(('A' + i), (j + 1 + nShift));
x = i;
y = j + nShift;
sCount++;
cout << "Search conducted at (" << i << ", " << (j + nShift) << ")" << endl;
}
if(nShift >= shovelSize - 1 || nShift > ROW) {
nShift = 0;
} else {
nShift++;
}
}
displayResults(sCount, found, x, y);
displaySearchPattern();
}
bool probeSandBoxTwo(char c, int i) {
if(sandbox[c-'A'][i-1] == 'X') {
return true;
} else {
return false;
}
}
void displayResults(int sCount, bool found, int x, int y) {
cout << endl;
cout << "Total searches: " << sCount << endl;
cout << endl;
if(found) {
cout << "Shovel found at coordinates: (" << x << ", " << y << ")" << endl;
}
}
void displaySandbox() {
cout << " ";
for(int i = 0; i < COL; i++) {
cout << (i % 10); //show index numbers [col]
}
cout << endl;
for(int i = 0; i < ROW; i++) {
cout << (i % 10) << " "; //show index numbers [row]
for(int j = 0; j < COL; j++) {
cout << sandbox[i][j];
}
cout << endl;
}
cout << endl;
}
void displaySearchPattern() {
int nShift = 0;
int shovelSize = 4;
cout << endl << " ";
for(int i = 0; i < COL; i++) {
cout << (i % 10); //show index numbers [col]
}
cout << endl;
for(int i = 0; i < ROW; i++) {
cout << (i % 10) << " "; //show index numbers [row]
for(int j = 0; j < COL; j++) {
if(!((j + nShift) % shovelSize)) {
cout << 'o';
} else {
cout << '.';
}
}
if(nShift >= shovelSize - 1 || nShift > COL) {
nShift = 0;
} else {
nShift++;
}
cout << endl;
}
}
void fillSandbox() {
for(int i = 0; i < ROW; i++) {
for(int j = 0; j < COL; j++) {
sandbox[i][j] = '.';
}
}
}
void placeShovel() {
srand(time(NULL));
int shovelRow,
shovelCol,
shovelSize = 4;
if(rand() % 2) {
//horizontal
shovelRow = rand() % ROW + 1;
shovelCol = rand() % (COL - (shovelSize - 1)) + 1;
for(int i = shovelCol - 1; i < shovelSize + (shovelCol - 1); i++) {
sandbox[shovelRow - 1][i] = 'X';
}
} else {
//vertical
shovelRow = rand() % (ROW - (shovelSize - 1)) + 1;
shovelCol = rand() % COL + 1;
for(int i = shovelRow - 1; i < shovelSize + (shovelRow - 1); i++) {
sandbox[i][shovelCol - 1] = 'X';
}
}
}
In this code, I also graphically display the pattern (when run) with which my algorithm searches.
Is this truly the optimal search pattern for such a scenario, is my implementation correct, and if so, why might I be having incorrect results returned?
A given test driver reports the following results:
The source code for this result (and its test driver).

Answer 1

found = false;
nShift = 0;
shovelSize = 4;
for(int i = 0; i < SandBoxRows; i++) {
for(int j = 0; (j + nShift) < SandBoxColumns; j+=shovelSize) {
found = probeSandBoxTwo(('A' + i), (j + 1 + nShift));
}
if(nShift >= shovelSize - 1 || nShift > SandBoxColumns) {
nShift = 0;
} else {
nShift++;
}
}
This corrects an error in the conditional portion of the for loop header which did not account for the index-shifting variable nShift.