CF95B Lucky Numbers [毒瘤分类讨论贪心/DFS]
其实代码用不着这么多goto，不过写着方便~
详细分析有时间再写吧
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| #include <iostream>
#include <algorithm>
#include <cstring>
#include <cstdio>
using namespace std;
const int MAXN = 1e5+10;
char a[MAXN],ans[MAXN];
int n;
int main(){
cin >> (a+1);
int n = strlen(a+1);
if(n & 1){
ODD_N:
for(int i = 1;i<=n/2 + 1;i++){
putchar('4');
}
for(int i = 1;i<=n/2 + 1;i++){
putchar('7');
}
putchar('\n');
}else{
int lead4 = 0,lead7 = 0,now = 1;
while(now <= n){
if(a[now] < '4'){
break;
}else if(a[now] == '4' && lead4 < n/2){
ans[now] = '4';
lead4++;
now++;
}else if(a[now] < '7' && lead7 < n/2){
ans[now] = '7';
lead7++;
break;
}else if(a[now] == '7' && lead7 < n/2){
ans[now] = '7';
lead7++;
now++;
}else{
goto TRY_LAST_USE_7;
}
}
if(false){
TRY_LAST_USE_7:
while(--now){
if(ans[now] == '4'){
lead4--;
}else{
lead7--;
}
if(ans[now] < '7' && lead7 < n/2){
ans[now] = '7';
lead7++;
goto OUTPUT;
}
}
goto ODD_N;
}
OUTPUT:
for(int i = 1;i<=lead4 + lead7;i++){
putchar(ans[i]);
}
for(int i = 1;i<=n/2 - lead4;i++){
putchar('4');
}
for(int i = 1;i<=n/2 - lead7;i++){
putchar('7');
}
putchar('\n');
}
}
|
