2020.2.15更新~~
这次用了栈，真滴灰常方便~果然人还是要多动脑筋呐
思路大致是：
1、用两个栈，一个记录数字，一个记录字符
2、遇到+，+号入字符栈，遇到-，将（-1）*后面的数字，入数字栈，+号入字符栈，因为提前用了下一个字符，要j++跳过下一个字符
3、x、/、直接处理计算的结果入数字栈，j++
4、根据字符栈中+号的个数循环，增加，最后的数字就是计算的结果
AC代码如下：
#include <stdio.h>
#include <stack>
#include <string>
#include <iostream>
using namespace std;
int main(){
int n;
int record[100];
stack<int>num;
stack<char>zifu;
string str;
scanf("%d",&n);
for(int i = 0;i <n;i++){
cin>>str;
while( !num.empty()){
num.pop();
}
while(!zifu.empty()){
zifu.pop();
}
for(int j = 0;j <str.size();j++){
if(str[j] - '0' >= 0 && str[j] - '0' <= 9){
num.push(str[j] - '0');
}
else{
if(str[j] == '+'){
zifu.push('+');
}
else if(str[j] == '-'){
num.push((str[j+1]-'0') * (-1));
zifu.push('+');
j++; //因为后一个数字已经被用掉了，防止重复，j++，下同
}
else if(str[j] == 'x'){
int t = num.top();
num.pop();
num.push(t*(str[j+1] - '0'));
j++;
}
else if(str[j] == '/'){
int s = num.top();
num.pop();
num.push(s/(str[j+1]- '0'));
j++;
}
}
}
while(!zifu.empty()){
int a = num.top();
num.pop();
int b = num.top();
num.pop();
num.push(a+b);
zifu.pop();
}
int ans = num.top();
num.pop();
record[i] = ans;
}
for(int i = 0;i <n;i++){
if(record[i] == 24){
printf("Yes\n");
}
else{
printf("No\n");
}
}
}
——————————————分割线——————————————
人生第一次C的代码写了200+行快300行。。。无他，if else穷举大法，居然一次AC了= =
事实上这一题用栈，构建后缀表达式是最好的算法，但我翻了书上那一块的代码也很长= =
没办法，太懒了，，改天再写栈的算法吧。。
好在这一题444=64，穷举了64个还可以忍受（其实复制粘贴到吐血= =），换成256那这题只有构建栈了
（这方法真是懒人方法，再说一遍并不推荐= =当然考试的时候能到分不就可以嘛）
AC代码：
#include <stdio.h>
#include <stack>
#include <vector>
#include <stdlib.h>
using namespace std;
int main(){
int a,b,c,d;
stack<int>st;
char f1,f2,f3; //三个符号
int n;
int linshi = 0; //临时存储结果
bool hhash[100] = {false};
scanf("%d",&n);
for(int i = 0;i <n;i++){
scanf("%d%c%d%c%d%c%d",&a,&f1,&b,&f2,&c,&f3,&d);
if(f1 == '+' ){
if(f2 == '+'){
if(f3 == '+'){
linshi = a+b+c+d;
}
else if(f3 == '-'){
linshi = a+b+c-d;
}
else if(f3 == 'x'){
linshi = a+b+c*d;
}
else{
linshi = a+b+c/d;
}
}
else if(f2 == '-'){
if(f3 == '+'){
linshi = a+b-c+d;
}
else if(f3 == '-'){
linshi = a+b-c-d;
}
else if(f3 == 'x'){
linshi = a+b-c*d;
}
else{
linshi = a+b-c/d;
}
}
else if(f2 == 'x'){
if(f3 == '+'){
linshi = a+b*c+d;
}
else if(f3 == '-'){
linshi = a+b*c-d;
}
else if(f3 == 'x'){
linshi = a+b*c*d;
}
else{
linshi = a+b*c/d;
}
}
else if(f2 == '/'){
if(f3 == '+'){
linshi = a+b/c+d;
}
else if(f3 == '-'){
linshi = a+b/c-d;
}
else if(f3 == 'x'){
linshi = a+b/c*d;
}
else{
linshi = a+b/c/d;
}
}
}
else if(f1 == '-' ){
if(f2 == '+'){
if(f3 == '+'){
linshi = a-b+c+d;
}
else if(f3 == '-'){
linshi = a-b+c-d;
}
else if(f3 == 'x'){
linshi = a-b+c*d;
}
else{
linshi = a-b+c/d;
}
}
else if(f2 == '-'){
if(f3 == '+'){
linshi = a-b-c+d;
}
else if(f3 == '-'){
linshi = a-b-c-d;
}
else if(f3 == 'x'){
linshi = a-b-c*d;
}
else{
linshi = a-b-c/d;
}
}
else if(f2 == 'x'){
if(f3 == '+'){
linshi = a-b*c+d;
}
else if(f3 == '-'){
linshi = a-b*c-d;
}
else if(f3 == 'x'){
linshi = a-b*c*d;
}
else{
linshi = a-b*c/d;
}
}
else if(f2 == '/'){
if(f3 == '+'){
linshi = a-b/c+d;
}
else if(f3 == '-'){
linshi = a-b/c-d;
}
else if(f3 == 'x'){
linshi = a-b/c*d;
}
else{
linshi = a-b/c/d;
}
}
}
else if(f1 == 'x' ){
if(f2 == '+'){
if(f3 == '+'){
linshi = a*b+c+d;
}
else if(f3 == '-'){
linshi = a*b+c-d;
}
else if(f3 == 'x'){
linshi = a*b+c*d;
}
else{
linshi = a*b+c/d;
}
}
else if(f2 == '-'){
if(f3 == '+'){
linshi = a*b-c+d;
}
else if(f3 == '-'){
linshi = a*b-c-d;
}
else if(f3 == 'x'){
linshi = a*b-c*d;
}
else{
linshi = a*b-c/d;
}
}
else if(f2 == 'x'){
if(f3 == '+'){
linshi = a*b*c+d;
}
else if(f3 == '-'){
linshi = a*b*c-d;
}
else if(f3 == 'x'){
linshi = a*b*c*d;
}
else{
linshi = a*b*c/d;
}
}
else if(f2 == '/'){
if(f3 == '+'){
linshi = a*b/c+d;
}
else if(f3 == '-'){
linshi = a*b/c-d;
}
else if(f3 == 'x'){
linshi = a*b/c*d;
}
else{
linshi = a*b/c/d;
}
}
}
else if(f1 == '/' ){
if(f2 == '+'){
if(f3 == '+'){
linshi = a/b+c+d;
}
else if(f3 == '-'){
linshi = a/b+c-d;
}
else if(f3 == 'x'){
linshi = a/b+c*d;
}
else{
linshi = a/b+c/d;
}
}
else if(f2 == '-'){
if(f3 == '+'){
linshi = a/b-c+d;
}
else if(f3 == '-'){
linshi = a/b-c-d;
}
else if(f3 == 'x'){
linshi = a/b-c*d;
}
else{
linshi = a/b-c/d;
}
}
else if(f2 == 'x'){
if(f3 == '+'){
linshi = a/b*c+d;
}
else if(f3 == '-'){
linshi = a/b*c-d;
}
else if(f3 == 'x'){
linshi = a/b*c*d;
}
else{
linshi = a/b*c/d;
}
}
else if(f2 == '/'){
if(f3 == '+'){
linshi = a/b/c+d;
}
else if(f3 == '-'){
linshi = a/b/c-d;
}
else if(f3 == 'x'){
linshi = a/b/c*d;
}
else{
linshi = a/b/c/d;
}
}
}
if(linshi == 24){
hhash[i] = true;
}
else{
hhash[i] = false;
}
linshi = 0;
}
for(int i = 0 ;i <n;i++){
if(hhash[i] == false){
printf("No\n");
}
else{
printf("Yes\n");
}
}
}
/*
10
9+3+4x3
5+4x5x5
7-9-9+8
5x6/5x4
3+5+7+9
1x1+9-9
1x9-5/9
8/5+6x9
6x7-3x6
6x4+4/5
1x8x3x1
*/
