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) ;elseprintf ("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){returnpow ((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] ;elsebreak ;}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] ;elsebreak ;}set[j] = temp ;}}}