题目大意：在平面上有n个点和一个值D，要求再长度为L的x轴上选出尽量少的点，使得对于给定的每个点，都有一个选出的点离它的欧几里德距离不超过D
解题思路：算出每个点的区间范围。区间的重叠部分由几个区间构成就有几个点满足要求。
;double L, D;int n;struct villages{double l, r;}vill[maxn];bool cmp(const villages a, const villages b) {if(a.r == b.r)return a.l < b.l;elsereturn a.r < b.r;}int main() {while(scanf(“%lf%lf”, &L, &D) == 2) {scanf(“%d”, &n);double x, y, len;for(int i = 0; i < n; i++) {scanf(“%lf%lf”, &x, &y);len = sqrt(D * D – y * y);vill[i].l = max(x – len,0.0);vill[i].r = min(L,x + len);}sort(vill, vill + n, cmp);int ans = 1;double r = vill[0].r;for(int i = 1; i < n; i++)if(r >= vill[i].l && r <= vill[i].r)continue;else{ans++;r = vill[i].r;}printf(“%d\n”, ans);}return 0;}
，当你能飞的时候就不要放弃飞
