平面内最近点问题C语言实现

  ....最近的作品,实在是少得可怜.

  不过还好,总比没有得要好.

  这个东西,是分治算法的例子,是按照思路实现起来的,总体说来,还算不错.希望接下来的,能实现得更自然.

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/* 10-16-11-01-22-23.17.c -- 第十章第十六题 */ /* 有问题存在,偶尔出现段错误.偶尔出现计算错误.这道习题耽误太久了,先不去研究了. -- 11-01-27-21.49 */ #include <stdio.h> #include <stdlib.h> #include <time.h> #include <math.h> #define SIZE (99) #define MAX (6000) #define INFINITY_DOUBLE (999999) typedef int Item ; typedef struct point { Item x_coordinate ; Item y_coordinate ; } Point ; int main (void) ; void initializeSet (Point * const set, const int size, const int max) ; /* ShortestDistance is the boxing of shortestDistance. */ double ShortestDistance (const Point * const set, const int size) ; double shortestDistance (const Point * const set_sorted_by_x, const Point * const set_sorted_by_y, const int left, const int right, const int size) ; double operose (const Point * const set, const int size) ; double distance (const Point * const pl, const Point * const pr) ; double minimum (const double l_num, const double r_num) ; double square (const int num) ; void shellSortAsX (Point * const set, const int size) ; void shellSortAsY (Point * const set, const int size) ; int main (void) { Point set[SIZE] ; int size = SIZE, max = MAX, index = 0, times = 100, i ; for (i = 0; i < times; i++) { initializeSet (set, size, max) ; if (ShortestDistance (set, size) != operose (set, size)) index++ ; } if (index) printf ("Wrong times is : %d./n", index) ; else printf ("All is OK./n") ; return 0 ; } void initializeSet (Point * const set, const int size, const int max) { int i ; srand ((unsigned int) time (NULL)) ; for (i = 0; i < size; i++) { set[i].x_coordinate = rand () % max + 1 ; set[i].y_coordinate = rand () % max + 1 ; } } double ShortestDistance (const Point * const set, const int size) { Point * set_sorted_by_x, * set_sorted_by_y ; double dist = INFINITY_DOUBLE ; int i ; if (NULL == set || size <= 0) { printf ("Failed in /"if (NULL == set || size <= 0)/"/n") ; return INFINITY_DOUBLE ; } set_sorted_by_x = (Point *) malloc (sizeof (Point) * size) ; if (NULL == set_sorted_by_x) { printf ("Failed in /"if (NULL == set_sorted_by_x)/"/n") ; return INFINITY_DOUBLE ; } set_sorted_by_y = (Point *) malloc (sizeof (Point) * size) ; if (NULL == set_sorted_by_y) { printf ("Failed in /"if (NULL == set_sorted_by_y)/"/n") ; free (set_sorted_by_x) ; return INFINITY_DOUBLE ; } for (i = 0; i < size; i++) { set_sorted_by_x[i] = set[i] ; set_sorted_by_y[i] = set[i] ; } shellSortAsX (set_sorted_by_x, size) ; shellSortAsY (set_sorted_by_y, size) ; dist = shortestDistance (set_sorted_by_x, set_sorted_by_y, 0, size - 1, size) ; free (set_sorted_by_x) ; free (set_sorted_by_y) ; return dist ; } double shortestDistance (const Point * const set_sorted_by_x, const Point * const set_sorted_by_y, const int left, const int right, const int size) { Point * strip ; double dl, dr, delta, boundary, temp, left_bracket, right_bracket ; int left_end, start, end, i, j, width ; /* Two points */ if (1 == right - left) return distance (set_sorted_by_x + left, set_sorted_by_x + right) ; /* Three points */ else if (2 == right - left) return minimum (distance (set_sorted_by_x + left, set_sorted_by_x + left + 1), distance (set_sorted_by_x + left + 1, set_sorted_by_x + right)) ; else { left_end = (left + right) / 2 ; dl = shortestDistance (set_sorted_by_x, set_sorted_by_y, left, left_end, size) ; dr = shortestDistance (set_sorted_by_x, set_sorted_by_y, left_end + 1, right, size) ; delta = minimum (dl, dr) ; boundary = set_sorted_by_x[left_end].x_coordinate ; /* Find out the start of the strip. */ if (delta > set_sorted_by_x[left_end].x_coordinate - set_sorted_by_x[left].x_coordinate) start = left ; else { temp = boundary - delta ; for (start = left; start < left_end; start++) { if (set_sorted_by_x[start].x_coordinate >= temp) break ; } } /* Find out the end of the strip. */ if (delta > set_sorted_by_x[right].x_coordinate - set_sorted_by_x[left_end].x_coordinate) end = right ; else { temp = boundary - delta ; for (end = left_end + 1; end < right; end++) { if (set_sorted_by_x[end].x_coordinate >= temp) break ; } } width = end - start ; /* Empty strip. */ if (1 == width) return delta ; /* There is only one point in the strip. */ else if (2 == width) return delta ; else { strip = (Point *) malloc (sizeof (Point) * (width + 1)) ; if (NULL == strip) { printf ("Failed in /"strip = (Point *) malloc (sizeof (Point) * (width + 1))/"/n") ; return INFINITY_DOUBLE ; } left_bracket = set_sorted_by_x[start].x_coordinate ; right_bracket = set_sorted_by_x[end].x_coordinate ; /* Copy. */ for (i = 0, j = 0; i < size; i++) { if (set_sorted_by_y[i].x_coordinate >= left_bracket && set_sorted_by_y[i].x_coordinate <= right_bracket) strip[j++] = set_sorted_by_y[i] ; } for (i = 0; i <= width; i++) { for (j = i + 1; j <= width; j++) { /* If Yi and Yj coordinates differ by more than delta. */ if (strip[j].y_coordinate - strip[i].y_coordinate > delta) break ; else if ((temp = distance (strip + i, strip + j)) < delta) delta = temp ; } } free (strip) ; } return delta ; } } double operose (const Point * const set, const int size) { double min = INFINITY_DOUBLE, temp ; int i, j ; for (i = 0; i < size; i++) { for (j = 0; j < size; j++) { if (j == i) continue ; else { if ((temp = distance (set + i, set + j)) < min) min = temp ; } } } return min ; } double distance (const Point * const pl, const Point * const pr) { return pow ((double) /* (x1 - x2) ^ 2 */ (square (pl -> x_coordinate - pr -> x_coordinate) + /* (y1 - y2) ^ 2 */ square (pl -> y_coordinate - pr -> y_coordinate)), 0.5) ; } double minimum (const double l_num, const double r_num) { return (l_num < r_num) ? l_num : r_num ; } double square (const int num) { return num * num ; } void shellSortAsX (Point * const set, const int size) { Point temp ; int i, j, increment ; for (increment = size / 2; increment > 0; increment--) { for (i = increment; i < size; i++) { temp = set[i] ; for (j = i; j >= increment; j -= increment) { if (temp.x_coordinate < set[j - increment].x_coordinate) set[j] = set[j - increment] ; else break ; } set[j] = temp ; } } } void shellSortAsY (Point * const set, const int size) { Point temp ; int i, j, increment ; for (increment = size / 2; increment > 0; increment--) { for (i = increment; i < size; i++) { temp = set[i] ; for (j = i; j >= increment; j -= increment) { if (temp.y_coordinate < set[j - increment].y_coordinate) set[j] = set[j - increment] ; else break ; } set[j] = temp ; } } }