POJ 2078

16ms 解法:

#include <cstdio>

//using namespace std;

int data[][];
int dp[][];
int row_min[];
int row_max[];

int n,min,max;

void solve(int row) {
    int i,j,pos,tmp, tmp_max;
    if (row == n) {
        max = dp[n-][];
        for (i = ; i < n; i++) {
            if (max < dp[n-][i]) {
                max = dp[n-][i];
            }
        }
        if (min > max) {
            min = max;
        }
        return;
    }

    //prune, the above max value + current line min value > current answer min, then return
    if (row_max[row-]+row_min[row]>min) {
        return;
    }

    for(i = ; i < n; i++) {

        //tmp_max cal current row's dp max value
        tmp_max = -;

        for (j = ; j < n; j++) {
            tmp = i+j;
            pos = tmp < n ? tmp : tmp-n;
            dp[row][pos] = dp[row-][pos] + data[row][j];

            if (dp[row][pos] > tmp_max) {
                tmp_max = dp[row][pos];
            }
        }
        row_max[row] = tmp_max;

        solve(row+);
    }

}

int main() {

    int i,j,val,mymin,mymax;

    while(scanf("%d", &n) && n != -) {

        for (i = ; i < n; i++) {
            mymin = ;
            for (j = ; j < n; j++) {
                scanf("%d", &val);
                data[i][j] = val;
                if (val < mymin) {
                    mymin = val;
                }
            }
            row_min[i] = mymin; //cal min value for every row
        }

        mymax = -;
        for (i = ; i < n; i++) {
            dp[][i] = data[][i];
            if (data[][i] > mymax) {
                mymax = data[][i];
            }
        }
        row_max[] = mymax;  //first row's max value

        min = ;
        solve();

        printf("%d\n", min);

    }
    return ;

}