题解 | 校门外的树

#include <stdio.h>

int main()
{
    int L = 0, M = 0,i = 0,j = 0;
    int l = 0, r = 0;
    scanf("%d %d",&L,&M);
    int arr[10001] = {0};
    for(i = 0; i < M; i++)
    {
        scanf("%d %d",&l,&r);
        for(j = l; j <= r; j++)
            arr[j] = 1;
    }
    int count = 0;
    for(i = 0; i <= L; i++)
    {
        if(arr[i] == 0)
            count++;
    }
    printf("%d",count);
    return 0;
}