Brush questions - Luogu -p1047 trees outside the school gate

P1047 Trees outside the school gate -C Language

1、 subject

2、 The problem solving process

(1) for the first time Did not notice the problem of repeated areas
result ：

Code ：

(2) The second time
result ：

Code ：

// Luogu 3 P1047  Trees outside the school gate 
#include <stdio.h>
#define TREE 10001// The maximum number of trees 
int main() {
    
	int l;// Road length 
	int m;// Number of areas  1<=m<=10
	int u,v;// Area value 
	int tree_num=0;// The total number of trees 
	int tree_value[TREE] = {
     0 };// Initialize the tree 
	int sum=0;// Number of roadside trees 
	int i;
	int j;
	scanf("%d %d", &l, &m);// Enter the length of the road and the number of areas 
	tree_num = l + 1;// The initial number of trees 
	for (i = 0; i < tree_num; i++) {
    // Mark the tree 
		tree_value[i] = 1;
	}
	for (i = 0; i < m; i++) {
    
		scanf("%d %d", &u, &v);
		for (j = u; j <= v; j++) {
    // Remove the trees in the area 
			tree_value[j] = 0;
		}
	}
	for (i = 0; i < tree_num; i++) {
    
		if (tree_value[i] == 1) {
    
			sum++;
		}
	}
	printf("%d", sum);
	return 0;
}