求解释 bool issafe这一块是什么意思？

[lmz569]

#include<stdio.h>

// Number of vertices in the graph
#define V 4

void printSolution(int color[]);

/* A utility function to check if the current color assignment
is safe for vertex v */
bool isSafe (int v, bool graph[V][V], int color[], int c)
{
for (int i = 0; i < V; i++)
if (graph[v][i] && c == color[i])
return false;
return true;
}

/* A recursive utility function to solve m coloring problem */
void graphColoring(bool graph[V][V], int m, int color[], int v)
{
/* base case: If all vertices are assigned a color then
return true */
if (v == V){
printSolution(color);
return;
}

/* Consider this vertex v and try different colors */
for (int c = 1; c <= m; c++)
{
/* Check if assignment of color c to v is fine*/
if (isSafe(v, graph, color, c))
{
color[v] = c;

/* recur to assign colors to rest of the vertices */
graphColoring (graph, m, color, v+1);


/* If assigning color c doesn't lead to a solution
then remove it */
color[v] = 0;
}
}

}

/* A utility function to print solution */
void printSolution(int color[])
{
printf(" Following are the assigned colors \n");
for (int i = 0; i < V; i++)
printf(" %d ", color[i]);
printf("\n");
}

// driver program to test above function
int main()
{
/* Create following graph and test whether it is 3 colorable
(3)---(2)
| / |
| / |
| / |
(0)---(1)
*/
bool graph[V][V] = {{0, 1, 1, 1},
{1, 0, 1, 0},
{1, 1, 0, 1},
{1, 0, 1, 0},
};
int m = 3; // Number of colors

int color[V];

for (int i = 0; i < V; i++)
color[i] = 0;

graphColoring(graph, m, color, 0);
return 0;
}