/*自己写的n^2算法... */#include <cstring>#include <cstdio>#include <iostream>#include <cmath>#include <algorithm>using namespace std;const int MAXN = 10000;double X[MAXN];double Y[MAXN];int n;double get_val(double dx, double dy) { return sqrt(dx*dx + dy*dy);}int main(){ #ifndef ONLINE_JUDGE freopen("in.txt", "r", stdin); #endif while(scanf("%d", &n) && n!=0) { for(int i=0; i<n; i++) { scanf("%lf%lf", &X[i], &Y[i]); } double min_len = MAXN; for(int i=0; i<n-1; i++) { for(int j=i+1; j<n; j++) { double dx = abs(X[i]-X[j]); if(dx >= min_len) continue; double dy = abs(Y[i]-Y[j]); if(dy >= min_len) continue; double val = get_val(dx, dy); if(val < min_len) min_len = val; } } if(min_len-MAXN > -1e-9) printf("INFINITY\n"); else printf("%.4lf\n", min_len); } return 0;}/*n^2算法，排序后剪枝(速度还可以)*/#include <cstring>#include <cstdio>#include <iostream>#include <cmath>#include <algorithm>using namespace std;const int MAXN = 10000;struct node{ double x, y;};node points[MAXN];int n;double get_val(double dx, double dy) { return sqrt(dx*dx + dy*dy);}bool cmp(node a, node b){ return a.x < b.x;}int main(){ #ifndef ONLINE_JUDGE freopen("in.txt", "r", stdin); #endif while(scanf("%d", &n) && n!=0) { for(int i=0; i<n; i++) { scanf("%lf%lf", &points[i].x, &points[i].y); } sort(points, points+n, cmp); double min_len = MAXN; for(int i=0; i<n-1; i++) { for(int j=i+1; j<n; j++) { double dx = points[j].x - points[i].x; if(dx >= min_len) break; double val = get_val(dx, points[i].y-points[j].y); if(val < min_len) min_len = val; } } if(min_len-MAXN > -1e-9) printf("INFINITY\n"); else printf("%.4lf\n", min_len); } return 0;}/*算法导论33章 分冶法 nlgn算法, 实现的不好...*/#include <cstring>#include <cstdio>#include <iostream>#include <cmath>#include <algorithm>using namespace std;const int MAXN = 10000;struct node{ double x, y;};node pointx[MAXN]; //按x坐标排序的数组int pointy[MAXN]; //按y坐标排序的数组int n;double get_val(double dx, double dy) { return sqrt(dx*dx + dy*dy);}double get_val(int i, int j) { double dx = pointx[i].x-pointx[j].x; double dy = pointx[i].y-pointx[j].y; return sqrt(dx*dx + dy*dy);}bool cmpx(node a, node b){ return a.x < b.x;}bool cmpy(int a, int b){ return pointx[a].y < pointx[b].y;}//分冶法double closePair(int l, int r){ if(r-l<=3) { //直接算 double min_len = MAXN; for(int i=l; i<r-1; i++) { for(int j=i+1; j<r; j++) { double val = get_val(i, j); if(val < min_len) min_len = val; } } return min_len; } int cury[MAXN]; memcpy(cury, pointy, sizeof(pointy)); int m = l + (r-l)/2; int p1=l, p2=m; for(int i=l; i<r; i++) { if(cury[i] < m) { pointy[p1++] = cury[i]; } else { pointy[p2++] = cury[i]; } } double min_val = min(closePair(l, m), closePair(m, r)); int leftx = pointx[m].x - min_val; int rightx = pointx[m].x + min_val; int cnt = 0; for(int i=l; i<r; i++) { if(pointx[pointy[i]].x >= leftx && pointx[pointy[i]].x <= rightx) { cury[cnt++] = pointy[i]; } } for(int i=0; i<cnt-1; i++) { for(int j=i+1; j<i+8 && j<cnt; j++) { min_val = min(min_val, get_val(cury[i], cury[j])); } } return min_val;}int main(){ #ifndef ONLINE_JUDGE freopen("in.txt", "r", stdin); #endif while(scanf("%d", &n) && n!=0) { for(int i=0; i<n; i++) { scanf("%lf%lf", &pointx[i].x, &pointx[i].y); } double min_len = MAXN; sort(pointx, pointx+n, cmpx); for(int i=0; i<n; i++) { pointy[i] = i; } sort(pointy, pointy+n, cmpy); min_len = closePair(0, n); if(min_len-MAXN > -1e-9) printf("INFINITY\n"); else printf("%.4lf\n", min_len); } return 0;}
