第一题 计算器的改良
大模拟，好好处理字符串。
第二题 税收与补贴
略过。
第三题 乘积最大
区间动归，记得高精度。
第四题 单词接龙
带字符处理的深搜。
代码
第一题
#include <stdio.h>
#include <ctype.h>
#include <string.h>
#define MAXN 300
char s[MAXN],c;
double xx,yy,x;
bool jia,havenum;
int wh;
int main() {scanf("%s",s);jia = 1;for (int i = 0;i < strlen(s);++i)if (s[i] == '=') {wh = i;break;}for (int i = 0;i < wh;++i)if (isdigit(s[i])) {havenum = 1;x = x * 10 + s[i] - '0';} else {if (isalpha(s[i])) {c = s[i];if ((!havenum) && (!x))x = 1;if (jia)xx += x;elsexx -= x;havenum = 0;x = 0;} else {if (havenum)if (jia)yy -= x;elseyy += x;if (s[i] == '+')jia = 1;elsejia = 0;x = 0;}}if (havenum)if (jia)yy -= x;elseyy += x;x = 0;havenum = 0;jia = 1;for (int i = wh + 1;i < strlen(s);++i)if (isdigit(s[i])) {havenum = 1;x = x * 10 + s[i] - '0';} else {if (isalpha(s[i])) {c = s[i];if ((!havenum) && (!x))x = 1;if (jia)xx -= x;elsexx += x;havenum = 0;x = 0;} else {if (havenum)if (jia)yy += x;elseyy -= x;if (s[i] == '+')jia = 1;elsejia = 0;x = 0;}}if (havenum)if (jia)yy += x;elseyy -= x;printf("%c=%.3lf\n",c,yy / xx);return 0;
}
第三题
#include <stdio.h>
#include <string.h>
#define MAXL 310
#define MAXN 50
#define MAXM 10
struct ss {int g[MAXL];
} f[MAXN][MAXM],a[MAXN][MAXN];
char s[MAXN];
int n,m;
ss bigger(ss a,ss b) {if (a.g[0] < b.g[0])return b;if (a.g[0] > b.g[0])return a;for (int i = a.g[0];i > 0;--i) {if (a.g[i] < b.g[i])return b;if (a.g[i] > b.g[i])return a;}return a;
}
ss cheng(ss a,ss b) {ss c;memset(c.g,0,sizeof(c.g));for (int i = 1;i <= a.g[0];++i) {int x = 0;for (int j = 1;j <= b.g[0];++j) {c.g[i + j - 1] += a.g[i] * b.g[j] + x;x = c.g[i + j - 1] / 10;c.g[i + j - 1] %= 10;}if (x)c.g[i + b.g[0]] += x;}c.g[0] = a.g[0] + b.g[0];while ((c.g[0] > 1) && (!c.g[c.g[0]]))--c.g[0];return c;
}
void out(ss a) {for (int i = a.g[0];i > 0;--i)printf("%d",a.g[i]);
}
int main() {scanf("%d%d",&n,&m);++m;scanf("%s",s);for (int i = n;i > 0;--i)s[i] = s[i - 1];for (int i = n;i > 0;--i) {a[i][i].g[0] = 1;a[i][i].g[1] = s[i] - '0';for (int j = i - 1;j > 0;--j) {a[j][i] = a[j + 1][i];a[j][i].g[++a[j][i].g[0]] = s[j] - '0';}}for (int i = 1;i <= n;++i)f[i][1] = a[1][i];for (int i = 1;i <= n;++i)for (int j = 2;j <= m && j <= i;++j)for (int k = j - 1;k < i;++k)f[i][j] = bigger(f[i][j],cheng(f[k][j - 1],a[k + 1][i]));out(f[n][m]);return 0;
}
第四题
#include <stdio.h>
#include <string.h>
#define MAXN 21
struct ss {char s[300];int len,time;
} a[MAXN];
int n,ans;
char te[30000010];
void find(int x) {if (x > ans)ans = x;for (int i = 1;i <= n;++i)if (a[i].time < 2)for (int j = 1;j < a[i].len;++j) {if (x - j < 0)break;bool can = 1;for (int k = 1;k <= j;++k)if (te[x - j + k] != a[i].s[k]) {can = 0;break;}if (can) {++a[i].time;for (int k = j + 1;k <= a[i].len;++k)te[x + k - j] = a[i].s[k];find(x + a[i].len - j);--a[i].time;}}
}
int main() {scanf("%d",&n);for (int i = 1;i <= n;++i) {scanf("%s",a[i].s);a[i].len = strlen(a[i].s);for (int j = a[i].len;j > 0;--j)a[i].s[j] = a[i].s[j - 1];}for (int i = 1;i <= n;++i) {for (int j = 1;j <= a[i].len;++j)te[j] = a[i].s[j];++a[i].time;find(a[i].len);}printf("%d\n",ans);return 0;
}