如何高效统计一个区间内离散数据的个数

[DragonII]

在一个区间范围内随机分布着大量离散的数据，如何能高效的统计出数据个数呢，大神们给个思路吧

[赵4老师]

仅供参考：

#include <stdio.h>
#include <string.h>
char s1[]="delete";
char s2[]="select";
unsigned char n[256]={0};
char r[257];
int i,L,o=0;
void main() {
    L=strlen(s1); for (i=0;i<L;i++) if (!n[(unsigned int)s1[i]]) n[(unsigned int)s1[i]]=++o;
    L=strlen(s2); for (i=0;i<L;i++) if (!n[(unsigned int)s2[i]]) n[(unsigned int)s2[i]]=++o;
    L=0;
	for	(o=1;o<=256;o++) {
		for	(i=0;i<256;i++)	{
			if (o==n[i]) {
				r[L++]=i;
				break;
			}
		}
		if (i>=256)	break;
	}
    r[L]=0;
    printf("[%s]\n",r);
}
//[deltsc]

[赵4老师]

再供参考：

//随机产生100000000个取值范围为[0～2的32次方减1]的数据，
//然后让用户输入一个数据，判断用户输入的数据是不是包含在前面随机产生的数据中。
//要求：当用户输入完成后，必须在1毫秒(千分之一秒)之内完成判断。
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <malloc.h>
long int i;
unsigned long ul;
unsigned long *d;
unsigned long ulrand(void) {
    return (
     (((unsigned long)rand()<<24)&0xFF000000ul)
    |(((unsigned long)rand()<<12)&0x00FFF000ul)
    |(((unsigned long)rand()    )&0x00000FFFul));
}
void main() {
    d=(unsigned long *)calloc(1<<(32-5),sizeof(unsigned long));
    if (NULL==d) {
        printf("Can not calloc(%d,%d)!\n",1<<(32-5),sizeof(unsigned long));
        return;
    }
    srand(time(NULL));
    for (i=0;i<100000000;i++) {
        while (1) {
            ul=ulrand();
            if (0==(d[ul>>5]&(1lu<<(ul%32)))) {
                d[ul>>5]|=1<<(ul%32);
                break;
            }
        }
        if (0==i%1000000) printf("%09d,%10lu\n",i,ul);
    }
    while (1) {
        printf("\nInput a number:");
        fflush(stdout);
        rewind(stdin);
        if (1==scanf("%lu",&ul)) break;
    }
    if (d[ul>>5]&(1<<(ul%32))) printf("Include.\n"    );
    else                       printf("Not include.\n");
    free(d);
}
//000000000,2135468533
//001000000,2465805973
//002000000,3844079964
//003000000,1883232874
//004000000,1204697784
//005000000,4050838287
//006000000,3802081245
//007000000,1586042671
//008000000,3119931368
//009000000, 251096899
//010000000,3491239701
//011000000,3365323844
//012000000,2191846708
//013000000,1879478195
//014000000,1112631457
//015000000,1927301519
//016000000,1717332861
//017000000,2922278240
//018000000, 694854106
//019000000, 273255526
//020000000, 398518467
//021000000,3270756812
//022000000,1500289424
//023000000,1502241936
//024000000,1770380660
//025000000,3668842116
//026000000,3255869879
//027000000,1299184024
//028000000,1072990028
//029000000, 242094712
//030000000,3789344297
//031000000,2599365925
//032000000, 962754138
//033000000,2055075654
//034000000,4083452879
//035000000, 489250842
//036000000, 611455230
//037000000, 277350616
//038000000,1597410795
//039000000,3224173662
//040000000,2291446877
//041000000,2546280575
//042000000,2509145642
//043000000,2371773252
//044000000, 635555963
//045000000,2674538666
//046000000,4253690312
//047000000,2675755514
//048000000,1269320296
//049000000,3172516920
//050000000,1430265210
//051000000, 196156173
//052000000,2470825669
//053000000,2536750977
//054000000,1182829949
//055000000,3202826434
//056000000,2263336265
//057000000, 313302924
//058000000,3630264578
//059000000,1154892716
//060000000,2985304230
//061000000,1252204837
//062000000,1292076720
//063000000, 242249250
//064000000,3999999961
//065000000, 431166416
//066000000,1366947236
//067000000,1414387330
//068000000,2143784481
//069000000,3242175409
//070000000,4158065163
//071000000,1425449573
//072000000,2493600232
//073000000,1316783455
//074000000,3723170478
//075000000,3064111466
//076000000, 408557403
//077000000,3722586955
//078000000,3801652651
//079000000,3788160154
//080000000,3329440047
//081000000,1408976868
//082000000, 471838899
//083000000,2145198260
//084000000,3781081738
//085000000,3439027738
//086000000,1150808750
//087000000,2782578638
//088000000,  85604584
//089000000,2704078162
//090000000, 584840269
//091000000,3854577719
//092000000,2823653537
//093000000, 797877025
//094000000,2248017755
//095000000,1787038685
//096000000,2816548567
//097000000, 489107494
//098000000, 911680090
//099000000,3677777147
//
//Input a number:3677777147
//Include.

[m0_45904445]

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