#include<stdio.h>
#include<stdlib.h>
int sum = 0;
int Danger(int r,int c, int(*a)[8])
  {

    for(int i=0;i<8;i++)
   {
       if(a[i][c])
      return 0;
    }
 for(int i=r,j=c;i>=0&&j>=0;i--,j--)
   {
     if(a[i][j])
     return 0;
   }
   for(int i=r,j=c;i>=0&&j<8;i--,j++)
  {
    if(a[i][j])
    return 0;
   }
     return 1;


 }
/*int Danger(int row, int j, int(*chess)[8]){
	int flag1 = 1, flag2 = 1, flag3 = 1, flag4 = 1, flag5 = 1;
	int ia, ib = 1, ic = 1, id = 1, ie = 1;
	for(ia = 0; ia < 8; ia++){
		if(*(*(chess + ia) + j) == 1){
			flag1 = 0;
			break;
		}else flag1 = 1;
	}
	
	while((row - ib) != -1 && (j - ib) != -1){
		if(*(*(chess + row - ib) + j - ib) == 1){
			flag2 = 0;
			break;
		}else flag2 = 1;
		ib++;
	}
	
	while((row + ic) != 8 && (j - ic) != -1){
		if(*(*(chess + row + ic) + j - ic) == 1){
			flag3 = 0;
			break;
		}else flag3 = 1;
		ic++;
	}
	
	while((row - id) != -1 && (j + id) != 8){
		if(*(*(chess + row - id) + j + id) == 1){
			flag4 = 0;
		}else flag4 = 1;
		id++;
	}
	
	while((row + ie) != 8 && (j + ie) != 8){
		if(*(*(chess + row + ie) + j + ie) == 1){
			flag5 = 0;
			break;
		}else flag5 = 1;
		ie++;
	}
/*	printf("%d", flag1);
	printf("%d", flag2);
	printf("%d", flag3);
	printf("%d", flag4);
	printf("%d", flag5);
	printf("\n");*/
	//printf("/");
/*	if(flag1 && flag2 && flag3 && flag4 && flag5){
		return 1;
	}else return 0;
} */
void EQ(int row, int col, int(*chess)[8]){
/*	int chess[8][8];
	for(int i = 0; i < 8; i++){
		for(int j = 0; j < 8; j++){
			chess[i][j] = pchess[i][j];
		}
	}*/
	if(row == 8){
		for(int i = 0; i < 8; i++){
			for(int j = 0; j < 8; j++){
				printf("%d ", *(*(chess + i) + j));
			}
					printf("\n");
		}
		printf("\n");
		++sum;
		return;
	}
	for(int j = 0; j < 8; j++ ){
		if(Danger(row, j, chess) == 1){
			*(*(chess + row) + j) = 1;
			EQ(row + 1, col, chess);
			*(*(chess + row) + j) = 0;
				/*	for(int i = 0; i < 8; i++){
					*(*(chess + row ) + i) = 0;
				}
				continue;*/
		}
		
	}
	
}

int main(){
	int chess[8][8];
	for(int i = 0; i < 8; i++){
		for(int j = 0; j < 8; j++){
			chess[i][j] = 0;
		}
	}
	EQ(0, 8, chess);
	printf("%d", sum);
	return 0;
}

When the first code is implemented, the main logic is not considered clearly, and only output after one round of circulation. The problem is that there is no backtracking.

for(int j = 0; j < 8; j++ ){
		if(Danger(row, j, chess) == 1){
			*(*(chess + row) + j) = 1;
			EQ(row + 1, col, chess);
			*(*(chess + row) + j) = 0;

To flash back

Recurse to the last line. After the output is successful, the original position trace should be erased. Otherwise, it will affect the judgment of the Danger function

*(*(chess + row) + j) = 0;