"Algorithmic Competition Primer Classic" "chapter three" after-school exercises (Part I)

After-school exercises the third wave came, to the third chapter after the code and the like a little bit longer, so I put this chapter of the answer into a few parts. This chapter focuses on the processing of strings, for string problems, usually as long as careful there is no problem, the following few said directly on the detailed.

Exercise 3-1 Score Statistics (STAT)

Task 1: This is straightforward on the code:

#include <stdlib.h> #include <stdio.h> #include <string.h> #define MAXN 10int cmp (const VOID*A,CON St Void*b) {return * (int*) A-* (int*) b;} int main () {int i,j,n,max,p;int stu[maxn],a[maxn]; memset (A,0,sizeof (a)); scanf ("%d", &n); for (i = 0; i < n; i++) {SCA NF ("%d", &p); a[p]++;} Max=a[0];for (i = 1; i < MAXN; i++) {if (A[i]>=max) {max=a[i];}} for (i = 0, j = 0; i < MAXN; i++) {if (A[i]==max) {stu[j++] = i;}} Qsort (Stu,j,sizeof (stu[0]), CMP), for (i = 0; i < J; i++) {if (i) printf ("");p rintf ("%d", Stu[i]);} printf ("\ n"); return 0;}

Task 2: This relative task 1 more difficult, one of the questions, in the use of the Qsort function, there is a small detail to note, that is, when the return, for double type to use the ternary operator, if the previous processing method will cause errors, the error from the floating point number error. My approach to this problem is similar to the first one, but I have to make a little sacrifice to be similar to the first integer, but I sacrificed the memory. The code is as follows:

#include <stdio.h> #include <string.h> #include <stdlib.h> #define MAXN 10000 + 100int cmp (const void*a, Const VOID*B) {return * (double*) a>* (double*) b?1:-1;} int main () {int i,j,a[maxn],n,max,temp;double p,stu[101];memset (a,0,sizeof (a)); scanf ("%d", &n); for (i = 0; i < n; i + +) {scanf ("%lf", &p); temp = 100*p;a[temp]++;} Max=a[0];for (i = 1; i < MAXN; i++) {if (A[i] > max) {max = A[i];}} for (i = 0, j = 0; i < MAXN; i++) {if (A[i]==max) {stu[j++] = (double) i/100;}} Qsort (Stu,j,sizeof (stu[0]), CMP), for (i = 0; i < J; i++) {if (i) printf ("");p rintf ("%.2lf", Stu[i]);} printf ("\ n"); return 0;}

Exercise 3-2 Word Length (word)

This problem is relatively simple, only need to pay attention to the number of words in the time to be careful of the better

#include <stdio.h> #include <ctype.h> #define MAXN 10000 + 100char Str[maxn];int main () {int i,sum = 0,count = 0; Count is used to record the number of spaces, sum is used to record the total number of letters of gets (STR), if (str[0]!= ') count = 1;for (i = 0; str[i]!= '; i++) {if (str[i]== ' && Isalpha (str[i+1])) count++;if (Isalpha (Str[i])) sum++;} printf ("count =%d,sum =%d\n", count,sum);p rintf ("%.2lf\n", 1.0*sum/count);    return 0;}

Exercise 3-3 the last three bits (product) of the product

In two steps, the first step is to discard the string containing the uppercase and lowercase letters, and the second part converts the string of pure numbers into numbers. The problem is clear and the code is as follows:

#include <stdio.h> #include <stdlib.h> #include <string.h>int isnum (char *a,int len) {int i;for (i = 0; I & Lt Len i++) {if (a[i]< ' 0 ' | | A[i]> ' 9 ') return 0;} return 1;} int main () {char Str[20];int i,n,p,tmp;//n represents the number of input integers, p represents the after three bits of the integer product (scanf ("%d", &n) = = 1) {p = 1;for (i = 0; i < n; i++) {scanf ("%s", str); GetChar (); if (Isnum (Str,strlen (str))) {TMP = atoi (str);p *= tmp;p%= 1000;}} printf ("%03d\n", p);}    return 0;}

For the other exercises in chapter three, the following article will continue

(If there is an error, please correct it)

"Algorithmic Competition Primer Classic" "chapter three" after-school exercises (Part I)