CodeForces 146C(脑洞)

问题描述:

Petya loves lucky numbers very much. Everybody knows that lucky numbers are positive integers whose decimal record contains only the lucky digits 4 and 7. For example, numbers 47, 744, 4 are lucky and 5, 17, 467 are not.

Petya has two strings a and b of the same length n. The strings consist only of lucky digits. Petya can perform operations of two types:

• replace any one digit from string a by its opposite (i.e., replace 4 by 7 and 7by 4);
• swap any pair of digits in string a.

Petya is interested in the minimum number of operations that are needed to make string a equal to string b. Help him with the task.

Input

The first and the second line contains strings a and b, correspondingly. Strings aand b have equal lengths and contain only lucky digits. The strings are not empty, their length does not exceed 105.

Output

Print on the single line the single number — the minimum number of operations needed to convert string a into string b.

Example

47

74

1

题目题意:给了俩个串，问最少操作次数使得a串变成b串

#include<iostream>#include<cstdio>#include<string>#include<cmath>using namespace std;int main(){    string str1,str2;    while (cin>>str1>>str2) {        int num1=0,num2=0,num3=0;        for (int i=0;i<str1.size();i++) {            if (str1[i]!=str2[i]) {                num3++;                if (str1[i]=='4') num1++;                else num2++;            }        }        int Min=min(num1,num2);        printf("%d\n",Min+num3-2*Min);    }    return 0;}