The original image link for this problem is broken, but based on the description: given an m*n matrix, find how many paths exist from point (0, 0) to point (m-1, n-1).
The movement rule is that each step can only go right or down from the current position.
Breadth-first search.
Here is the code:
AC on the first try. The code performance is probably not optimal.
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| struct PPoint {
int x;
int y;
};
class Solution {
public:
bool CheckIn(int x, int y, PPoint *p, int top) {
for(int i = 0; i < top; i++) {
if(x == p[i].x && y == p[i].y) {
return true;
}
}
return false;
}
int uniquePaths(int m, int n) {
int **map = new int*[m];
for(int i = 0; i < m; i++) {
map[i] = new int[n];
}
for(int i = 0; i < m; i++) {
for(int j = 0; j < n; j++) {
map[i][j] = 0;
}
}
map[0][0] = 1;
PPoint *p = new PPoint[m+n];
PPoint *p_c = new PPoint[m+n];
int index = 0;
p[index].x = 0;
p[index++].y = 0;
while(true) {
int top = 0;
for(int i = 0; i < index; i++) {
int x = p[i].x;
int y = p[i].y;
if(x + 1 < m) {
map[x+1][y] += map[x][y];
if(CheckIn(x+1, y, p_c, top) == false) {
p_c[top].x = x+1;
p_c[top++].y = y;
}
}
if(y + 1 < n) {
map[x][y+1] += map[x][y];
if(CheckIn(x, y+1, p_c, top) == false) {
p_c[top].x = x;
p_c[top++].y = y+1;
}
}
}
if(top == 0) break;
index = top;
for(int i = 0; i < top; i++) {
p[i].x = p_c[i].x;
p[i].y = p_c[i].y;
}
}
return map[m-1][n-1];
}
};
|