挑战程序设计竞赛笔记_P55

//理解的时候一定要看打出来的表理解！！！

#include
#include
#define max(a, b) a > b ? a : b
const int MAX_N = 100;
const int MAX_W = 10000;
int n, W, w[MAX_W], v[MAX_N], dp[MAX_N + 1][MAX_W + 1];
int rec1(int i, int j)
{
memset(dp, -1, sizeof(dp));
if (dp[i][j] >= 0)
return dp[i][j];
if (i == n)
return 0;
if (j < w[i])
return dp[i][j] = rec1(i + 1, j);
else
return dp[i][j] = max(rec1(i + 1, j), rec1(i + 1, j - w[i]) + v[i]);
}
int rec2(int i, int j)
{
memset(dp, -1, sizeof(dp));
if (dp[i][j] >= 0)
return dp[i][j];
if (i == 0)
return 0;
if (j < w[i - 1])
return dp[i][j] = rec2(i - 1, j);
else
return dp[i][j] = max(rec2(i - 1, j), rec2(i - 1, j - w[i - 1]) + v[i - 1]);
}
int arr1()
{
memset(dp, 0, sizeof(dp));
for (int i = n - 1; i >= 0; i--)
{
for (int j = 1; j <= W; j++)
{
if (j < w[i])
dp[i][j] = dp[i + 1][j];
else
dp[i][j] = max(dp[i + 1][j], dp[i + 1][j - w[i]] + v[i]);
}
}
return dp[0][W];
}
int arr2()
{
memset(dp, 0, sizeof(dp));
for (int i = 1; i <= n; i++)
{
for (int j = 1; j <= W; j++)
{
if (j < w[i - 1])
dp[i][j] = dp[i - 1][j];
else
dp[i][j] = max(dp[i - 1][j], dp[i - 1][j - w[i - 1]] + v[i - 1]);
}
}
return dp
[W];
}
int arr3()
{
//数组方法3，同2
memset(dp, 0, sizeof(dp));
for (int i = 0; i < n; i++)
{
for (int j = 1; j <= W; j++)
{
if (j < w[i])
dp[i + 1][j] = dp[i][j];
else
dp[i + 1][j] = max(dp[i][j], dp[i][j - w[i]] + v[i]);
}
}
return dp
[W];
}
int arr4(){
memset(dp, 0, sizeof(dp));
for (int i = 0; i < n; i++){
//这里从j=1开始不行！！因为dp[i+1][j+w[i]]中j=0是有用的！而之所以前面的那些个数组方法可以，是因为他们根本用不着j=0来推断右下的元素
for (int j = 0; j <= W; j++){
if (w[i] + j <= W){
dp[i + 1][j + w[i]] = dp[i][j] + v[i];
}
dp[i + 1][j] = max(dp[i][j], dp[i + 1][j]);
// if (w[i] + j <= W){
//     dp[i + 1][j + w[i]] = max(dp[i + 1][j + w[j]], dp[i][j] + v[i]);
// }//这个改动是不是666？
}
}
return dp
[W];
}
void print()
{
printf(" i\\j");
for (int i = 0; i <= W; i++)
printf("%4d", i);
putchar(10);
for (int i = 0; i <= n; i++)
{
printf("%4d", i);
for (int j = 0; j <= W; j++)
printf("%4d", dp[i][j]);
putchar(10);
}
putchar(10);
}
int main()
{
freopen("E:/My/input.txt", "r", stdin);
scanf("%d%d", &n, &W);
for (int i = 0; i < n; i++)
scanf("%d%d", w + i, v + i);

printf("arr1:%d\n", arr1());
print();

printf("arr2:%d\n", arr2());
print();

printf("arr3:%d\n", arr3());
print();

printf("arr4:%d\n", arr4());
print();

// printf("rec1:%d\n", rec1(0, W));
// print();

// printf("rec2:%d\n", rec2(n, W));
// print();

return 0;
}